(2013·山西四校二模)Studies show that students often ________ to too much pressure tend to develop mental problems.

A．exposing

B．being exposed

C．to expose

D．exposed

水平仪是用来测量工件、部件（）的量具。精度为0.02mm/m的水平仪，表示气泡每移动一格，被测长度1米的两端高低相差（）。