Exchange of answerbacks act s a confirmation that the messages（）at the destination.

A.have received

B.have been received

C.are received

D.are being received

方药配伍寓有"金水相生"之意的方剂是（）

A.百合固金汤

B.六味地黄丸

C.归脾汤

D.养阴清肺汤

E.清燥救肺汤