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
网友回答
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。