单选题 He was ______ when he became president of the corporation.
A. at his forty B. in his forty
C. of his forties D. in his forties

【正确答案】 D

【答案解析】[解析] be in his forties在他四十多岁时。在这个结构中，注意介词用in，数字用复数。十几岁应说in one’s teens。从二十多岁到九十多岁分别应说：in one’s twenties，…，in one’s nineties。同样，在20世纪80年代、90年代，分别应说：in the 1980s，in the1990s。分别读作in the nineteen eighties，in the nineteen nineties。