—Tom must be at home because the light in his house is on. —Hebe at home because I saw hi

问题补充：

—Tom must be at home because the light in his house is on.

—Hebe at home, because I saw him playing basketball on the playground.

A. must B. can’t C. mustn’t

答案：

解析：句意:-Tom一定在家里因为他家里的灯亮着。-他不可能在家，意为我看见他在操场打篮球了。根据这个情景可知，这里两个人是在进行推测，根据第二个人的话可知，他很确定Tom不在家里，表示否定的推测应该用can’t,意思是不可能。must 表示推测时只能放在肯定句中。故选B。