问题
选择题
—Tom must be at home because the light in his house is on.
—He ____ be at home, because I saw him playing basketball on the playground.
A. must B. can’t C. mustn’t
答案
答案：B
由 I saw him playing basketball on the playground（我之前看见他正在操场上打篮球）
可知Tom不可能在家
A一定B不可能C禁止
故选B