By the time they reached the bus stop, the bus__________ for ten minutes.
A:had left
B:have left
C:had been away
D:have been away
晴朗的白天进入植物体叶片气孔和从叶片中通过气孔散失的气体依次是( )
摘录某同学实验记录本中有关实验现象的记录,其中肯定有误的是( )