.-- His father is a professor and has been teaching in the university for more than twenty

问题补充：

.-- His father is a professor and has been teaching in the university for more than twenty years.

-- .

A. So is his mother

B. So has his mother

C. So his mother does

D. So it is with his mother

答案：

A. So is his mother

B. So has his mother

C. So his mother does

(答案→)D. So it is with his mother

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