Teachers should create an environment     children are taught how to solve problems of learning by themselves.

A．why

B．where

C．which

D．whose

提单的作用有：（）

A.提单是托运人与承运人之间订有运输合同的凭证

B.提单是承运人从托运人处收到货物的凭证

C.提单是代表货物所有权的物权凭证

D.承运人收到货物重量证明