问题补充：
His sister left home in 1998, and since.
A. had not been heard of
B. has not been heard of
C. had not heard of
D. has not heard of
答案：
A. had not been heard of
(答案→)B. has not been heard of
C. had not heard of
D. has not heard of
解析：句意为：他的妹妹在1998年离开家，自从那时就没有音讯了。用现在完成时的否定结构。
