A:鳃
B:气囊
C:气管
D:皮肤
一条根能不断地伸长,是由于( )
The fire started on the second floor and it wasn't long ______ the whole building was burned down.
黄河是中华民族的母亲河.读图,下列有关黄河流域的说法,正确的是( )