Either you or one of your students ________ to attend the meeting that is due tomorrow.

A．are B

B．is

C．have

D．be

判断地脚螺栓的状况如何，很难用目视观察来完成，首先要刮干净地脚螺栓与基础混凝土及容器底座间的接触处，仔细检查此部位的腐蚀状况。用锤子侧面敲击全部（）。