Hawking became world-famous in .A. his thirties in the 1970’s B. the thirties in his 1970

问题补充：

Hawking became world-famous in .A. his thirties in the 1970’s B. the thirties in his 1970C. his 30s in 1970’sD. the thirties during the 1970

答案：

in one’s thirties 在某人三十多岁时，in/during the 1970s意思是“在二十世纪七十年代”。