.He has to finish the experiment today. He must be in the lab ?---That s quite possibl

问题补充：

.--- He has to finish the experiment today. He must be in the lab,?

---That s quite possible.

A. mustn he

B. won he

C. doesn he

D. isn he

答案：

A. mustn he

B. won he

C. doesn he

D. isn he

解析：该题考查反意疑问句中尾句部分的助动词用法，must be结构中的中心词应为be，且He must be in the lab 相当于I think he is in the lab，故其尾句部分为isn he。