It was Asimov was eleven years old his talent for writing became obvious.
A. that, when
B. When, which
C. when, when
D. when, that
网友回答
A. that, when
B. When, which
C. when, when
(答案→)D. when, that
解析：句意：当Asimov11岁时，就他的写作天赋就非常明显了。这里是强调句型，被强调的是when引导的时间状语从句，判断强调句型的方法是把It was that这三个词去掉，整个句子不缺成分，意思完整。故选D。