Tom never loses heart in face of difficulties he always tries his best to overcome them.

问题补充：

Tom never loses heart in face of difficulties, ,he always tries his best to overcome them.

A. On the other hand

B. On the contrary

C. At the same time

D. As a result

答案：

A. On the other hand

(答案→)B. On the contrary

C. At the same time

D. As a result

解析：短语辨析。A另一方面；B恰恰相反；C同时；D结果是。句意：面对困难时，Tom从未丧失信心。恰恰相反，他总是努力克服 。故B正确。