to得加个宾语,所以where引导to的宾语从句,它自己作为从句中的地点状语
这句相当于I’ve read up to the place where the children discover the secret cave.
或者I’ve read up to the place in which the children discover the secret cave.
反正都是不用that的.
that引导宾语从句是不在从句中做成分的
He told that he would go to the college the next year
他告诉我他下一年上大学.