one out of.One out of every twenty students____dropped from the course each term.A.is B.are请问,这里为什么是A呢.

one out of.One out of every twenty students____dropped from the course each term.A.is B.are请问,这里为什么是A呢.
one out of.
One out of every twenty students____dropped from the course each term.
A.is B.are
请问,这里为什么是A呢.

one out of.One out of every twenty students____dropped from the course each term.A.is B.are请问,这里为什么是A呢.
主语是"ONE OUT OF EVERY TWENTY SS" 每20个学生当中有一个,表示一个学生怎么怎么样,是单数

因为这里的中心词是one
所以用单数

one out of是几分之一 是单数不是复数，所以选A