问题

The number of the children in the school ________ about three hundred. ________ of them________ from the countryside.
A:is; 20 percents; are
B:is; 20 percent; are
C:are; 20 percent; is
D:are; 20 percents; are;
B:is; 20 percent; are
C:are; 20 percent; is
D:are; 20 percents; are;
正确答案是: