It was        Asimov was eleven years old        his talent for writing  became obvious.

1. A.
   that, when
2. B.
   When, which
3. C.
   when, when
4. D.
   when, that

It was ______ Asimov was eleven years old ______ his talent for writing became obvious.

   A. that; when   B. when; that    C. that; that    D. when; when

.

It was_________Asimov was eleven years old________ his talent for writing became obvious.

A. that, when  B. When, that        C. when, when              D. when, which

It was        Asimov was eleven years old        his talent for writing                        became obvious.

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