问题补充:
Not only his parents but also his brother to the Summer Palace. They haven’t been back.
A. have been
B. have gone
C. has been
D. has gone
答案:
A. have been
B. have gone
C. has been
(答案→)D. has gone
解析:D Not only …but also…遵循“就近原则”,即连接两个主语时,谓语动词的单复数与最近的主语一致。本句与his brother一致,因为去了颐和园还没回来,故用has gone。