819.What disappointed us was that their determination finally ________.

A.gave off

B.gave out

C.gave up

D.gave in

820. There were so many people shopping in the mall that we _______soon after entered it.

A.got lost

B.got involved

C.got separated

D.got concerned

819.答案是B;

give off发出，放出fgive out分费,公布，公开，用完，耗尽；give up放弃，自首; I give in 屈服，让步。此处表示他们没有决心,令人失望。

820.答案是C;

根据语境，此处表示走散，分开。