关于句子结构分析问题
问题描述：
关于句子结构分析问题
The tubes were attached to a long stick which helped keep the rocket moving in a straight direction.
这个句子感觉有些奇怪,我说一下我的理解,a long stick是先行词which helped做定语从句,那么helped已经是从句中的动词了,为什么还会出现keep the rocket doing?
这样keep和help岂不是让从句中有了两个谓语?
答
省略了to 其实是helped (to) keep