The farm________ we learned to feed cattle two years ago has changed a lot.

A．when

B．which

C．that

D．where

下列行为中，构成无因管理的是（）。

A.未受委托替朋友招待客人

B.未成年人抢救落水儿童

C.主动代同事值夜班

D.代替配偶放弃继承权