A:how often are we going to be away
B:how often we are going to be away
C:how long are we going to be away
D:how long we are going to be away
在一个点电荷形成的电场中,关于电场强度和电势的说法中正确的是( )
“开元年间,左右藏库,财物山积,不可任数。四方丰稔,百姓殷富。”材料直接反映了唐朝开元年间( )
读《五带划分图》