How close parents are to their children _____ a strong influence

How close parents are to their children _____ a strong influence on the development of the children’s character. (QE0904-43)
A、have
B、has
C、having
D、had
【正确答案】:B
【题目解析】:主语是:How close parents are to their children,为单数,要 have 使用三单形式 has .