The company had about 20 notebook computers, but only one-third

The company had about 20 notebook computers, but only one-third _____used regularly.


A、is
B、are
C、was
D、were
【正确答案】：D
【题目解析】：本题考查时态和主谓一致。句意：这家公司大约有20台笔记本电脑，但是只有三分之一经常被使用。一般来讲，分数作主语时，谓语用单数。但是由前半句about 20 notebook computers可知，此处用复数。本句的时态是过去时，因此应该用were。