A:溶质质量增加
B:溶剂质量减少
C:溶液质量不变
D:溶质质量分数减少
John didn't feel well yesterday; otherwise he ______ to see his friend off at the airport. ( )
经济特区是我国对外开放的前沿,我国设立经济特区的根本目的是( )