Passenger pigeons once     1    （fly）over much of the United States in unbelievable numbers. Written     2    （account）from the 18th and 19^th centuries described flocks（群）so large that they darkened the sky for hours.

It     3    （calculate）that when its population reached its     4    （high）point, there were more than 3 billion passenger pigeons—a number equal to 24 to 40 percent of     5    total bird population in the United States, making it     6    （true）the most abundant bird in the world. However, the population decreased because of     7    （commerce）hunters who killed them by the thousands. Americans' need for wood scattered the flocks and forced the birds to go farther north ,     8    cold temperatures and spring storms contributed to their decline.

In 1897, the state of Michigan tried to pass a law prohibiting the killing of passenger pigeons, only     9    （find）that by then, no sizable flocks had been seen in the state for 10 years. The last of them, known affectionately     10    Martha, died at the Cincinnati Zoological Garden on September 1, 1914.

Jane Goodall was born in London in 1934. She became interested in animal stories when she was a very young child. She always dreamed of working with wild     1     (animal).   When she was eleven years old, she decided that she wanted     2     (go) to Africa to live with and write about animals. But this was not the kind of thing young women usually did in the 1940s. Everybody was laughing except her mother. “If you     3     (real) want something, you work hard, you take advantage of the opportunity, you never give up,and you will find a way,” her mother said to her. The opportunity     4     (come) at last. A school friend invited her to Africa. Jane worked as     5     waitress until she got enough money to travel there.

In 1957, Jane Goodall traveled to Africa. She soon met the well-known scientist Louis Leakey and began working for him as an assistant. He later asked her to study a group of chimpanzees     6     (live) by a lake in Tanzania. Very little was known about wild chimpanzees at that time.

Jane spent many years studying chimpanzees     7     this area of Africa. It was no easy work. They were very shy     8     would run away when she came near. She learned to watch them from far away using binoculars (双筒望远镜). Over time, she slowly gained     9     (they) trust. Watching the chimpanzees, she made many discoveries. They ate vegetables and fruit. But she found that they also ate meat. A few weeks later, she made an even more     10     (surprise) discovery. She saw chimpanzees making and using tools to help them catch insects.

Sleep experts recommend teenagers get 8 to 10 hours of sleep every night. Many college students experience     1     (regular) and insufficient sleep.

David Creswell, professor of MIT, led a team of researchers to evaluate     2     relationship between sleep and grade point average (GPA).

"Animal studies so far     3     (show) how critical sleep is for learning and memory," said Creswell, "Here we show how this work translates to humans. The     4     (little) nightly sleep a first year college student gets at the beginning of the school term predicts lower GPA at the end of the term. Lack of sleep may be hurting students'     5     (able) to learn in their college classrooms."

The study evaluated more than 600 first-year students across five studies at three universities. The students wore wrist Fitbit devices     6     (monitor) and record their sleep patterns. The researchers found that students in the study sleep on average 6. 5 hours a night.

More     7     (surprise), the researchers found that students who receive less than six hours of sleep experienced a pronounced decline in academic performance.

"Once you start dipping below six hours, you are starting to accumulate massive sleep debt     8     can harm a student's health and study habits,    9     (damage) the whole system," said Creswell. "Most surprising to me was that no matter     10     we did to make the effect go away, it continued."

A new research shows that nicer people are likely to be poorer than people who are not so nice. Researchers studied how the personalities of different people    1    (affect) how rich they were. They found that people    2     a nice and warm personality were     3    (poor)than people who were more selfish. They also found that it was more difficult for kinder people to look after their money because of their “agreeableness”. The research suggests that agreeableness    4    (associate) with various signs of financial hardship, including lower savings and higher debt.

Researchers looked at data from different    5    ( source), including two online surveys taken by almost 4,000 participants. The data included answers to questions on people's financial situation    6     people’s attitude towards money. They compared this data with findings of some other surveys, in    7    almost 5,000 people answered questions about their personality and their agreeableness. The researchers say agreeable people seem    8    (care) less about money so they do not manage their money    9    (wise). Researcher Sandra Matz says that    10    (be) kind has "financial costs " but that kinder people “always have a happier life”.