In Patton City, days are categorized as having heavy rainfall (more than 2 inches), moderate rainfall (more than one inch, but no more than 2 inches), light rainfall (at least at trace, but no more than one inch), or no rainfall. In 1990, there wre fewer days with right rainfall than in 1910 and fewer with moderate rainfall, yet total rainfall for the year was 20% higher in 1990 than in 1910.
If the statements above are true, then it is also possible that in Patton City
a. the number of days with heavy rainfall was lower in 1990 than in 1910.
b. the number of days with some rainfall, but no more than 2 inches, was the same in 1990 as in 1910
c. the number of days with some rainfall, but no more than 2 inches, was higher in 1990 than 1910.
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
e. the average amount of rainfall per month was lower in 1990 than in 1910.
答案选a,可是我不大想得通。请教应该是怎样的解题思路呀？ | 
