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
网友回答
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 1970's 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。