-----I wonder if you could go with me to the supermarket.

------- Don’t disturb me. I _____________my experiment report all the morning and haven’t finished yet.

A．write

B．was writing

C．have written

D．have been writting

在夹具上安装工件时，工件在夹具中、夹具在机床上、夹具相对于刀具都应该保持一定的（）

A、相对位置

B、正确位置

C、正确精度

D、正确尺寸