— I think ______ of the materials I listened to at the beginning of the exam ______ easy.

— I think so.

A．three fourths, is

B．third four, are

C．three fourths, are

D．three fourth, are

如果百分表头的大指针正好指在“O”处，说明被测工件的孔径（缸径）（）其校表尺寸。

A.等于

B.大于

C.小于

D.不能判断