Our friends were _______ busy ______ with each other _______the time.

A．so; talking; that they forgot

B．too; talking; to forget

C．too; to talk; to forget

D．so; to talk; that they forgot

换热器循环水出入口的温差上升是由于（）。

A.循环水量增加

B.循环水量减少

C.循环水入口温度升高

D.循环水出口温度下降