A is correct
There are only two likely possibilities for 1990 to have more total rainfalls than 1910:
1) Total rainfalls from heavy rainfalls is bigger in 1990 than in 1910. This could be done either by very heavy rains in a few days in 1990 or with more heavy rainfalls days in 1990
2) Total rainfalls from moderate/light rainfalls is bigger in 1990 than in 1910. This possibility sounds counterintuitive but is mathmatically possible. Keep in mind the definition of moderate/light rainfalls is based on a range. It is conceivable that a moderate rainfalls day could have either 1.9 inch or 1.1 inch of rain. So if all the moderate rainfall days in 1990 had 1.9 inch while all the moderate rainfall days in 1910 had only 1.1 inch, the total rainfall in 1990 could be bigger than in 1910.
Answer A points out the first possibility and is the right answer.
-- by 会员 sdcar2010 (2011/4/13 0:06:37)
多谢sdcar，很厉害的NN，一直无私指点CDers，每每拜读你的解释都要读很多遍才懂，哈不过精华就是这样。这题和我以前遇到的不一样，possible，选的是可能有机会正确的，其余全是不可能发生的？？对不？其实对于这题我有疑惑的是D选项，因为两个年份只是moderate rainfall的day不同，或者说1910比1990天数多，但因为每天的平均降雨量（inch）不知道所以1990的moderate rainfall的总降雨量（我把它理解成D中的
total number of inches of rain）
还是可能比1910的多的。那么D. the total number of inches of rain that fell on days with moderate rainfall in 1990 was more than twice what it had been in 1910
也有可能对，但后来又想到m r的范围是（1,2）所以不可能超过两倍，不知道我理解有没有误？
-- by 会员 爱吃巧克力 (2011/4/28 19:02:44)
