A:who; who
B:that; which
C:who; that
D:who; which
中学时代,许多同学开始写日记,这是从_______方面观察和认识自己。( )
气体在容积固定的密闭容器中并且温度升高时,下列说法正确的是( )
若ab=|ab|,则必有( )