做托里拆利实验时,可以确认管内进入了少量空气的现象是( )
A:将管在水银槽中轻轻上提,管内水银柱高度不变
B:管内水银柱高度略小于760 mm
C:使管倾斜,管内水银柱长度增加
D:无论怎样使管倾斜,水银都不能充满全管
Jane got up late this morning,so she had to take a ____ to school.