问题补充：
The output of the gold mine is now four times it was before liberation.
A. that
B. what
C. which
D. than
答案：
A. that
(答案→)B. what
C. which
D. than
解析：考查倍数表达方式。倍数表达方式有 A is four time as big as B=A is four times the size of B=A is three times bigger than B=A is four times what B is.对照结构，选择B
