A:was he able to make himself hear
B:he was able to make himself hear.
C:he was able to make himself heard
D:was he able to make himself heard .
下列各种现象中,属于山区常见的自然灾害的是( )
甲苯能够使酸性KMnO4溶液褪色是因为( )
①试管内液面上升
②试管内溶液变红
③试管内液面不上升
④试管内溶液变蓝
⑤试管内溶液不变色.