Do pigeons use their biological clocks to help them find directions from the sun? We can keep pigeons in a room lit only by lamps. And we can program the lighting to produce artificial "days", different from the day outside. After a while we have shifted their clocks. Now we take them far away from home and let them. go on a sunny day. Most of then stat out as if they know just which way to go, but choose a wrong direction. They have picked a direction that would be correct for the position of the sun and the time of day according to their shifted clocks.

We have talked about one of the more complex experiments that lead to the belief that homing pigeons can tell directions by the sun. But what happens when the sky is darkly overcast by clouds and no one can see where the sun is? Then the pigeons still find their way home. The same experiment has been repeated many times on sunny days and the result was always the same. But on very overcast days. clock-shifted pigeons are just as good as normal pigeons in starting out in the right directions. So it seems that pigeons also have some extra sense of direction to use when they cannot see the sun.

Naturally, people have wondered whether pigeons might have a build—in compass- something that would tell them about the directions of the earth's magnetic field. One way to test that idea would be to see if a pigeon's sense of direction can be fooled by a magnet attached to its back. With a strong magnet close by. a compass can no longer tell direction.

26. relating to the natural processes of living things (Para.1)

27. give a set of instructions for performing an operation (Para. 1)

28. changed slightly (Para.1)

29. difficult to understand because of having many different part(Para. 1)

30. the feeling of certainty that something is true (Para.2)

31. dark with clouds (Para.2)

32. done more than once (Para.2)

33. usual and typical (Para.2)

34. an instrument that shows directions (Para.3)

35. tricked into believing (Para.3)

(46.When smoking amongst women was not as widespread as it is now, women were considered to be almost free from cardiovascular diseases and lung cancer. Unhappily, the situation has changed, and smoking kills over half a million women each year in the industrialized world.) But it is also an increasingly important cause of ill health amongst women in developing countries 

(47.A recent World Health Organization (WHO) consultation on the statistical aspects of tobacco-related mortality concluded that the toll that can be attributed to smoking throughout the world is 2.7 million deaths per year.) It also predicted that if current patterns of cigarette smoking continue unchanged the global death toll from tobacco by the year 2025 may increase to eight million deaths per year. A large proportion of these will be amongst women. 

(48. Despite these alarming statistics the scale of the threat that smoking poses to women's health has received surprisingly little attention. Smoking is still seen by many as a mainly male problem, perhaps because men were the first to take up the habit and therefore the first to suffer the ill effects. ) This is no longer the case. Women who smoke like men will die like men. WHO estimates that in industrialized countries, smoking rates amongst men and women are very similar, a around 30 per cent; in a large number of developed countries. smoking is now more common among teenage girls than boys. 

As women took up smoking later than men, the full impact of smoking on their health has yet to be seen. But it is clear from countries where women smoked longest, such as the United Kingdom and the United States. that smoking causes the same diseases in women as in men and the gap between their death rates is narrowing. (49. On current trends. some 20 to 25 per cent of women who smoke will die from their habit. One in three of these deaths will be among women under 65 years of age.) The US Surgeon General has estimated that, amongst these women, smoking is responsible for around 40 per cent heart disease deaths, 55 per cent of lethal strokes and, among women of all ages, 80 per cent of lung cancer deaths and 30 per cent of all cancer deaths. Over the last 20 years, death rates in women from lung cancer have more than doubled in Japan, Norway, Poland, Sweden and the United Kingdom: have increased by more than 200 per cent in Australia, Demark and New Zealand; and have increased by more than 300 per cent in Canada and the United States. 

There are dramatically increasing trends in respiratory cancer among women in developed countries, and the casual relationship of smoking, rather than air pollution and other factors, to lung cancer is very clear. (50. In the United States. for instance, the mortality rate for lung cancer among female non-smokers has not changed during the past 20 years. During the same period, the rate among female smokers has increased by a factor of half. ) In South East Asia, more than 85 per cent of oral cancer cases in women are caused by tobacco habits.

Paragraph Ten

If you sit at a desk all day, get up frequently and walk around. If you carry a heavy shoulder bag. make sure to carry it on both your right and left shoulder, switching off as each gets tired. Even better: wear a cross-body bag. These and other tips will help you avoid bad posture.

Tips for m_____ good posture.

Paragraph Seven

An analysis across the EU showed that nearly 1/5 British families are headed by a single adult. And while 18.4% of families in this country have a solo parent, numbers come to just 12.7% in Germany. 14.4% in France and 10.6% in the Netherlands. In Belgium the share is 16.1%. In Ireland, it is 18.1%.

The p____ of single-parent families in European countries.

Paragraph Nine

A survey of more than 285.000 US high school students carried out between 1991 and 2012 found young people had fewer friends with whom to interact, but less desire for more friends. The research has also shown that teenagers have fewer friends than 20 years ago, despite the increasing popularity of social media.

U____ to make more friends.

Paragraph Eight

The eating habits of American children appear to be shifting. The news is good. Burgers. fries and colas remain popular with the under-13 set, of course, But new market research shows that consumption of these foods at restaurants is declining, while soup, yogurt, fruit, grilled chicken and chocolate milk are on the rise.

A c______ for the better in the eating habits of American children.

Paragraph Four

Mr Devlin, 46, from Nunhead, London, is living with a bizarre condition called prosopagnosia, meaning he struggles to recognize faces 一even those of his own family. Mr Devlin is a painter. He has to memorise his family's voices and body language in order to know who they are, but reading voices and body language doesn't always work.Mr.

Devlin is s____ from face blindness.

Paragraph Five

How dogs react to TV一whether it's running around, barking excitedly, or just ignoring it — may come down to personality or breed. Hunting dogs. which are driven by smell, aren't as interested in visuals, but herding breeds, such as terriers, may be more stimulated by moving objects they see on the small screen.

Breed a _____ dogs' reactions to TV.

Paragraph Six

A recent study has found that people who use an iPhone are cleverer than those who prefer Android devices. This is based on research that found states with more college graduates also tend to have higher iPhone sales. The study discovered that Alaska, Montana and Vermont have the largest number of iPhone users in the US. These states also have the highest percentage of college graduates.

iPhone users are s______.

Paragraph Two

Doctors should refrain from adding patients as friends on Facebook, they should not hug or allow patients to call them by their first names, regulators have warned. Blurring the lines between social and professional relationships can impact on the level of care offered and prevent patients from being honest about important side effects.

C_____ relationships may hinder objective care.

Paragraph Three

Researches suggest that for healthy older adults. even though their memory might not be as good, they can naturally recruit other brain regions that are not typically involved in shopping. Scientists discovered older shoppers use an additional brain area to remember competing consumer products and choose the better one — meaning they don't miss a bargain.

Shopping is b____ to one’s brainpower.