单项选择题

Questions 23 to 25 are based on the conversation you have just heard.

A．It may endanger the life on the earth and in space.
B．The investment is vast more than we can afford.
C．It is prohibited to use nuclear explosions in space.
D．The technologies of using nuclear are underdeveloped.
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单项选择题
A．The inactive period of flu is longer.B．The symptoms of flu develop suddenly.C．The symptoms of flu are lighter.D．The flu is harder to catch.
A．The inactive period of flu is longer.
B．The symptoms of flu develop suddenly.
C．The symptoms of flu are lighter.
D．The flu is harder to catch.
填空题
Researchers have found that people’s mental abilities peak at 22 before beginning to deteriorate just five years later. The results suggested that (36) designed to prevent or (37) age-related conditions may need to start earlier, long before people become pensioners. Almost half of over 50s are unaware of leading cause of blindness . Results focus on a conclusion that some (38) of age-related cognitive decline begin in healthy, educated adults when the yare in their 20s and 30s. The study of 2,000 men and women lasted for over seven years. The respondents, aged between18-60, were asked to solve (39) puzzles, recall words and story details and spot (40) in letters and symbols. Similar tests are often used to (41) mental disabilities and declines, including dementia. The research by the University of Virginia found that in 9 out of 12 tests the (42) age at which the top performance was achieved was 22. The first age at which performance was (43) lower than the peak scores was 27--for three tests of reasoning, speed of thought and spatial visualisation. (44) However, another report found that (45) increased until at the age of 60. (46) , including Jimi Hendrix, Jim Morrison, Brian Jones, Janis Joplin and Kurt Cobain.
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