求问一道数学题，始终转不过弯。。

yayapku

是在模考的时候遇到的

When 1000 children were inoculated with a certain vaccine, some developed inflamation at the site of inoculation,  and some developed fever. How many children developed inflammation but not fever?

A) 880 children developed neither inflammation nor fever
B) 20 children developed fever

答案是两个一起sufficient, 请问是怎么算出来的呢。。。为啥我总觉得两个一起也不充分啊。。。求大神指教，拜谢！！！