问答题 有一种南瓜平均重2．5 kg，另一个品种平均重1 kg。两个品种的杂交后代(F1)平均重1．75 kg。F1之间杂交得到200个F2，质量在1～2．5 kg之间，其中3个重2．5 kg左右，3个重1 kg左右。有多少对基因控制这两种南瓜的质量?每一对基因有多大的作用?

单项选择题 第一篇 Crystal Ear One day a friend asked my wife Jill if I wanted a hearing aid. 'He certainly does, 'replied Jill. After hearing about a remarkable new product, Jill finally got up the nerve to ask me if I'd ever thought about getting a hearing aid. 'No way,' I said. 'It would make me look 20 years older.' 'No, no,' she replied. 'This is entirely different. It's Crystal Ear!'Jill was right. Crystal Ear is different--not the old-styled body worn or over-the-ear aid, but an advanced personal sound system so small that it's like contacts (隐性眼镜) for your ears. And Crystal Ear is super-sensitive and powerful, too. You will hear sounds your ears have been missing for years. Crystal Ear will make speech louder, and the sound is pure and natural.I couldn't believe how tiny it is. It is smaller than the tip of my little finger and it's almost invisible when worn. There are no wires, no behind-the-ear device. Put it in your ear and its ready-to-wear mold (形状) fits comfortably. Since it's not too loud or too tight, you may even forget that you're wearing it! Use it at work or at play. And if your hearing problem is worse in certain situations, use Crystal Ear only when you need it.Hearing loss, which occurs typically prior to teenage years, progresses throughout one's lifetime. Although hearing loss is now the world's number one health problem, nearly 90 percent of people suffering hearing loss choose to leave the problem untreated. For many millions, treating hearing loss in a conventional way can involve numerous office visits, expensive testing and adjustments to fit your ear. Thanks to Crystal Ear, the 'sound solution' is now convenient. Almost 90 percent of people with mild hearing loss, and millions more with just a little hearing drop-off (下降), can be dramatically helped with Crystal Ear. Moreover, its superior design is energy-efficient, so batteries can last months. Crystal Ear is now available to help these people treat their hearing loss with a small hearing amplifier (放大器). 第 31 题 Initially the writer did not want to buy a hearing aid becauseA． it would make him look old.B． it would make him nervous.C． it was too expensive.D． it was old-styled.

单项选择题 Exercising Your Memory 1 Aging does not mean a dramatic decline in memory power, unless you help ithappen by letting your mind go.2 That's not to say that memory doesn't change throughout life. Researchers dividememory into categories based on the length of time when memories are stored. Onesystem divides it up as short-term (less than one minute; remembering a telephonenumber while you dial, for instance), long-term (over a period of years) and verylong-term memory (over a lifetime).3 Short-term memory isn't mastered until about age 7, but after that you never lose it. Long-term memory, however, involves more effort and skill and changes more through life. It's not until the early teens (十几岁) that most people develop a mature long-term memory.4 First, we must get information into our heads through learning. Learning strategies can get rusty (生锈的) without constant use. High school and college students, who are forced to repeatedly exercise their long-term memory abilities (at least long-term enough to get them through a final exam), usually do well on memory tests. The longer you stay in school, the more chance you get to polish your learning, skills. It's no wonder that more highly educated people have more effective memory skills throughout life.5 Although older people in general learn somewhat more slowly than they did-whenyounger, a dramatic difference exists between those who stay intellectually active --reading, discussing, taking classes, thinking -- and those who do not. Giving the brain a daily workout (锻炼) is just as important as exercising your muscles. Brainwork keeps your learning strategies in shape, and this helps your memory to function at full capacity.6 The next part of a healthy long-term memory is retention (记忆力), the ability to store what you have learned. Memory researchers still do not know whether memories are lost--whether they still exist in the brain but our mental searching cannot turn them up, or have disappeared entirely as our brain ages.7 The third necessity for memory is recall, the ability to bring to mind the memories we have stored. Again, while aging has widely different effects on the recall abilities of different people, research indicates that the older we get, the longer it takes to recall facts. But slower recall is still recall. In fact, aging does not seem to have any effect on forgetting at all, which takes place at the same rate in younger and older people. 第 23 题 Paragraph 3＿＿＿＿＿＿＿