He pretended to be French, but his German accent _______.

A．gave him up

B．gave him off

C．gave him out

D．gave him away

在酒精（C₂H₅OH）和水（H₂O）的混合液中，酒精的质量为15kg，水的质量为25kg，混合物的平均分子量为（）。

A.23.32

B.24.15

C.26.78

D.26.21