He felt that medicine was the most important cause to which he could dedicate himself
问题描述：
He felt that medicine was the most important cause to which he could dedicate himself
请问,这是病句吗?为什么多了一个 " TO "
答
不是病句.
因为主句要表达的是 medicine was the cause to something,
从句which并不是要补充说明cause,而是补充说明something.那，去掉TO可以吗你可以把which开始的从句替换成一个单词，来看句子是否仍旧成立。
medicine was the cause to recover. 如果把to去掉，就变成，
medicine was the cause recover.显然不对。
而recover的位置现在需要用一句话来代替，即
he could dedicate himself。
就成了原句里的medicine was the cause to which
he could dedicate himself.