题目

孟德尔用豌豆进行杂交实验时，对母本的处理是 A、先去雄后授粉               B、先授粉后去雄 C、不去雄只授粉               D、只去雄不授粉 答案：AWhen the world was a simpler place, the rich were fat, the poor were thin, and right-thinking people worried about how to feed the hungry .Now, in much of the world, the rich are thin, the poor are fat, and right-thinking people are worrying about fatness. Evolution (进化) is mostly to blame . It has designed mankind to deal with lack, not plenty. People are perfectly fit to store energy in good years to see them through lean ones. But when bad times  never come , they are stuck  with that energy , stored around their expanding bellies (腹部). Thanks to rising agricultural productivity, lean years are rarer all over the globe. According to the UN , the number of people  short of food fell from 920m in 1980 to 799m 20 years later , even though the world 's population increased by 1.6 billion over the period . This is mostly a cause for celebration. Mankind has won what was, for most of his time  on this planet , his biggest battle: to ensure that he and his offspring（后代） had enough to eat . But every silver lining has a cloud , and the result of prosperity (繁荣) is a new trouble. Fatness is the world 's biggest public-health topic today —the main cause of heart disease, which kills more people these days than AIDS, malaria, war, the major risk factor in diabetes (糖尿病) ; heavily connected with cancer and other diseases . Since the World Health Organization labeled fatness an "epidemic (流行病)" in 2000, re­ports on its fearful results have come thick and fast . Will public-health warnings, combined with media pressure, persuade people to get thinner, just as they finally put them off tobacco? Possibly. In the rich world, sales of healthier foods are booming and new figures suggest that over the past year Americans got very slightly thinner for the first time in recorded history. But even if Americans are losing a few ounces, it will be many years before the country solves the health problems caused by half a century ' s dining to overload . And, everywhere else in the world, people are still piling on the pounds. That's why there is now an agree­ment among doctors that governments should do something to stop them. 1．What's the main idea the writer intends to tell us in this passage?     A．It's harmful to have enough to eat.     B．It's better to be thin than fat.     C．Fatness is the greatest danger in the world.     D．Fatness has become a great health problem. 2．It can be inferred from the passage that the biggest problem in history is _______ .     A．people were thin                        B．people smoked heavily     C．there was not enough food to eat           D．people stored energy in good years 3．Why does the author compare smoking with the fatness problem in this passage?     A．They are both problems difficult to settle.     B．They both lead to the same diseases.     C．They are both bad habits.     D．They are both harmful to health. 4．Which of the following is true according to this passage?     A．Man has got rid of lean years by raising agricultural productivity.     B．Though difficult, man may break away from the fatness problem.     C．Fatness may cause many diseases such as heart disease, AIDS and cancer.        D．The doctors feel that they can do nothing about the fatness problem.