Great scientists（Period 7 Assessment）
the idea that all stress makes you sick also takes no notice of what we know about people.it is supposed that we’re all weak and passive in the face of difficulty.but many come through periods of stress with more physical and mental strength than they had before.we also know that a long time without change or challenge can lead to boredom and physical and mental damage.
55.the studies on stress in the early 1970’s led to __________.
a.wide spread worry over its harmful effects
b.great fear about the mental problems it could cause
c.a deep research into illnesses connected with stress
d.popular avoidance of stressful jobs
56.according to the passage people who have experienced ups and downs may become __________.
a.discouraged when faced with difficulty
b.physically and mentally weak
c.more experienced in the face of difficulty
d.uninterested in what happens to them
57.what’s the purpose of writing the text?
a.to tell people the discoveries about stress.
b.to tell people how to keep healthy.
c.to help people avoid stressful events.
d.to help people view stress properly.
答案：55～57 a c d
d
i’m gwen outen with the voa special english development report.
a few years ago, researchers discovered a simple answer to a big problem.they found that the bacteria that causes cholera can be removed from drinking water with simple cloth filters.pouring water from rivers or lakes through several thicknesses of cloth can trap tiny organisms like the cholera bacteria.
a three-year study took place in bangladesh.american and bangladeshi scientists went to 65 small villages in a country where cholera is a major health problem.they tested the use of saris as cloth filters.a sari is the traditional clothing worn by most women in bangladesh.
people in one group of villages used cloth from old saris, folded eight times, as a filter for their drinking water.people in another group of villages used modern nylon filters for their water.people in the other villages continued to gather water in traditional ways, without using filters.about 44 000 people were studied in each of the three groups of villages.
rita colwell from the university of maryland at college park helped lead the study.she said the people in the villages using filters from old saris had the lowest number of cases of cholera.the researchers also found that almost 99 percent of cholera bacteria could be filtered out with the sari cloth.rita colwell said cloth from old saris worked best because it has been washed repeatedly.she said the space between the threads of the material narrows when the cloth is washed, so it traps smaller particles.