It is requested that each of the teachers invited      a performance at the party.

A．should give

B．will give

C．has to give

D．must give

工程测量用经纬仪的主要功能是( )。

A．测量两点间的高差

B．测量两个方向之间的水平夹角

C．测量待定点的高程

D．测量两点间的水平距离