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

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

(答案→)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。