在使用显微镜时，可用来调节光线强弱的部件是 [ ]
A．粗准焦螺旋
B．转换器
C．遮光器
D．细准焦螺旋
答案：C
He _____and his friends took her to hospital just now.[ ]
A. felt excited
B. became interested
C. became happy
D. felt sick
数控机床中相互作用的零件之间由于松动和偏差将产生（）。
A.零点偏移
B.复位
C.反向间隙
D.刀具偏置
