Jane has ______ from school for 2 years. When she ______ the happy time, she always misses her teachers and classmates.
南、北美洲的分界线是( )
如图所示,为电场中一条电场线,一个点电荷由静止开始,只在电场力作用下,从A点移到B点,下面论述正确的是( )