Harry Potter fans were left in shock author J．K-Rowling revealed she regretted pairing Granger and Ron in the novel．
A. what
B. when
C. since
D. before
网友回答
A. what
(答案→)B. when
C. since
D. before
解析：句意：当作者J．K-Rowling披露她后悔在小说中让Granger 和 Ron成为一对的时候，哈利波特的粉丝很惊讶。这里需要when引导时间状语从句，“当…时候”，what“什么”，since“自从”before“在…前”，都不符合句意。所以选B。