—May I speak to Tom please?—But he for work an hour ago.A. set aboutB. set offC. took o

问题补充：

—May I speak to Tom, please?

—But he for work an hour ago.

A. set about

B. set off

C. took off

D. took over

答案：

A. set about

(答案→)B. set off

C. took off

D. took over

解析：短语辨析。A开始做某事；B引爆，使…发生;使…开始；C脱掉，起飞；D接管；句意：—我可以找Tom说话吗？—但是一个小时前就开始工作了。根据句意说明B正确。