你举的例子 you must put the book where you found it
的确是状语从句.
但是不用that引导的也不一定就是状语从句,比如:
You must put the book to the place where you found it.
这是个定语从句 where = from which
“而且定语从句中 如果后面是个完整的句子,并且是that引导的,那肯定是同位语从句.”
基本正确.看你对后面完整句子的理解,有时候that 可以在从句中作主语,它还是个定语从句,例如:
This is the precious diamond that will be exhibited tommorrow.
这就是明天要展出的那颗珍贵的钻石.that 引导定语从句,在从句中作主语.