In he began to learn Russian when he was in . A. 1970; the 50’sB. the 1970; his 50s C.

问题补充：

In , he began to learn Russian, when he was in .

A. 1970; the 50’s

B. the 1970; his 50s

C. the 1970s; his fifties

D. 1970s; his fifties

答案：

A. 1970; the 50’s

B. the 1970; his 50s

(答案→)C. the 1970s; his fifties

D. 1970s; his fifties

解析：句意：在十九世纪七十年代，当他已经五十几岁的时候，他开始学习俄语。固定词组“在20世纪70年代” in the 1970s 和in the 1970s都可以，“在某人几十岁的时候”in one’s+几十的复数，如：in his 20s在他20几岁的时候，所以选C。