Tom began to learn Russian by himself in .A. the fiftyB. the fiftiesC. his fiftiesD. his f

问题补充：

Tom began to learn Russian by himself in .

A. the fifty

B. the fifties

C. his fifties

D. his fifty

答案：

A. the fifty

B. the fifties

(答案→)C. his fifties

D. his fifty

解析：in one’s fifties在某人五十多岁时。另外，注意：in the 1990’s表示“在二十世纪90年代”。