I won’t tell the student the answer to the math problem until he ______ on it for more than an hour.

A．has been working

B．will have worked

C．will have been working

D．had worked

蓄电池指示数据在1.75～1.5伏之间说明（）。

A.该单格完好

B.应充电

C.蓄电池有故障