---The students sitting at the back can’t see the blackboard________.

---Why not_________ them move a little forward?

A．clear enough, let

B．enough clear, letting

C．clearly enough, let

D．enough clearly, letting

下面型号中，截面积最小的带是（）。

A、A型带

B、SPB型带

C、SPZ型带

D、C型带