Đáp án và giải thích

Now I would like to introduce to you the list of presentations during the following week so you can better plan your schedule.

The first presenter Simon is one of our best ski instructors. As an experienced instructor, he will inform you about the dangers that face skiers and snowboarders. Accidents happen mostly to those who are careless or ignorant. Good risk management involves considering both the probability and consequences of an accident.

The next speech titled Solution is given by Jamie Kurt. A list of problems may occur to novice skiers and snowboarders, so he is going to offer useful information for first timers on choosing the appropriate gears, the right dress code and ways of protecting your skin. For instance, some of you may have rented the skiing equipment, but rental footwear is notoriously uncomfortable. Then Jamie will provide instructions to help make your footwear fit better.

The third speech is about a documentary introducing skiing and snowboarding and the difference between the two sports. It also depicts a group of snow lovers exploring new slopes with breath-taking views. The director Andy Fisher will be there, addressing the whole shooting experience.

The fourth talk is about the tricks of skiing, presented by Harry Tyson. It is most useful for those who have already tried skiing, yet still need more practice to master the sport. Harry will teach you how to turn more skillfully. A lot of people can keep their skis roughly parallel but there's no point if you make it hard to work with and slide around out of control. Useful exercises will also be suggested to improve your parallel skiing technique so that you can tackle steeper slopes and enjoy yourself more.

Johnson Smith will be the last presenter, mainly addressing towards advanced skiers. He manages to apply snow climbing into skiing. Climbing in soft snow, you are floundering around. Walking becomes harder, so a good trick during climbing is to maintain a wider gait, approximately shoulder width, so that you are more stable while walking. This works for skiing as well.

Đáp án và giải thích

You will hear two health studies students, Lucy and Sam, talking about the topic of vitamin supplements.

Now listen carefully and answer questions 21 to 26.

Lecturer: OK, we’ve looked at the history of vitamin supplements and thought about why people take them. We’ve also considered the reasons why some health professionals are critical of the vitamin supplement industry. Now work with a partner and discuss the key issues.

Lucy: Sam, shall we work together?

Sam: Sure. Let’s go over the history.

Lucy: Well, before the 1900s, when someone became weak and tired, and it wasn’t clear why, doctors assumed they were suffering from an infection – like a virus.

Sam: Or they’d been in contact with something poisonous or harmful. Something they’d handled or eaten. Doctors had no other explanation for it.

Lucy: But in the early 1900s, that changed. That researcher in the US - Joseph Goldberger, – he realised people who basically lived off corn – they were getting ill because they weren’t eating anything else.

Sam: Exactly. And other researchers were realising the same thing. Like, in places where people only ate white rice – they were suffering from a disease called beriberi.

Lucy: So the researchers concluded that there must be something missing – that the stuff some people were eating had no nutritional value. And from there, researchers began to identify vitamins – like A and B – for the first time.

Sam: A huge scientific breakthrough.

Lucy: So doctors, the public,... everyone got to hear about vitamins – first that they existed, and second, you needed them to be healthy.

Sam: But it was governments that were really worried about vitamin deficiency. Certainly in the US and in the UK, at least.

Lucy: What do you mean?

Sam: Well, in the 1930s those governments were worried about people’s general health, because everyone was suddenly buying canned fruit, artificial butter, meat in tins... that kind of thing. It became very common. And so newspapers were featuring lots of government reports about how serious this was.

Lucy: I see.

Sam: And then, some people saw a business opportunity.

Lucy: Naturally.

Sam: In the 1940s, companies started making and selling vitamin supplements in bottles. And they decided the easiest way to market them was to target housewives.

Lucy: Why was that? Because housewives were responsible for keeping families healthy?

Sam: I’d say so. In the weekly magazines housewives read, the companies made exaggerated claims about what the supplements could do, and they showed pictures of rats in a laboratory before and after they were given vitamins. The ‘before’ pictures showed the rats looking very sick.

Lucy: So they scared the housewives into buying their product.

Sam: Apparently.

Lucy: But vitamins were still expensive, weren’t they? It wasn’t until the 1950s that more people could afford to buy them.

Sam: Why was that?

Lucy: Well manufacturers had discovered how to produce vitamins artificially and in enormous quantities in their factories.

Sam: I suppose that’s what goes on with any product. It starts expensive until manufacturers adapt their technology. Were there any developments in the 1960s?

Lucy: Companies changed their promotional strategy to increase their sales. They used movie stars to say how effective the supplements were.

Sam: That’s still true today. Celebrity endorsement really seems to work. Someone on the TV says vitamins have made them healthier and immediately more consumers go out and buy them.

Đáp án và giải thích

Hi. Today we’re going to be looking at animals in urban environments and I'm going to be telling you about some research on how they're affected by these environments.

Now, in evolutionary terms, urban environments represent huge upheavals, the sorts of massive changes that usually happen over millions of years. And we used to think that only a few species could adapt to this new environment. One species which is well known as being highly adaptable is the crow, and there've been various studies about how they manage to learn new skills. Another successful species is the pigeon, because they're able to perch on ledges on the walls of city buildings, just like they once perched on cliffs by the sea.

But in fact, we’re now finding that these early immigrants were just the start of a more general movement of animals into cities, and of adaptation by these animals to city life. And one thing that researchers are finding especially interesting is the speed with which they’re doing this – we’re not talking about gradual evolution here – these animals are changing fast.

Let me tell you about some of the studies that have been carried out in this area. So, in the University of Minnesota, a biologist called Emilie Snell-Rood and her colleagues looked at specimens of urbanised small mammals such as mice and gophers that had been collected in Minnesota, and that are now kept in museums there. And she looked at specimens that had been collected over the last hundred years, which is a very short time in evolutionary terms. And she found that during that time, these small mammals had experienced a lump in brain size when compared to rural mammals. Now, we can’t be sure this means they’re more intelligent, but since the sizes of other parts of the body didn’t change, it does suggest that something cognitive was going on. And Snell-Rood thinks that this change might reflect the cognitive demands of adjusting to city life - having to look in different places to find food, for example, and coping with a whole new set of dangers.

Then over in Germany at the Max Planck Institute, there's another biologist called Catarina Miranda who's done some experiments with blackbirds living in urban and rural areas. And she's been looking not at their anatomy but at their behaviour. So as you might expect, she's found that the urban blackbirds tend to be quite bold – they’re prepared to face up to a lot of threats that would frighten away their country counterparts. But there's one type of situation that does seem to frighten the urban blackbirds, and that's anything new – anything they haven't experienced before. And if you think about it, that's quite sensible for a bird living in the city.

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Jonathan Atwell, in Indiana University, is looking at how a range of animals respond to urban environments. He’s found that when they’re under stress, their endocrine systems react by reducing the amount of hormones such as corticosterone into their blood. It’s a sensible-seeming adaptation. A rat that gets scared every time a subway train rolls past won’t be very successful.

There's just one more study I'd like to mention which is by Sarah Partan and her team, and they’ve been looking at how squirrels communicate in an urban environment, and they've found that a routine part of their communication is carried out by waving their tails. You do also see this in the country, but it's much more prevalent in cities, possibly because it's effective in a noisy environment.

So what are the long-term implications of this? One possibility is that we may see completely new species developing in cities. But on the other hand, it’s possible that not all of these adaptations will be permanent. Once the animal’s got accustomed to its new environment, it may no longer need the features it's developed.

So, now we've had a look ...