一座高6 m的水塔顶端渗水,每隔一定时间有一滴水滴落下。当第5滴离开水塔顶端时,第1滴水滴正好落到地面,则此时第3滴水滴距地面的高度为_______m。
4.5
I work in a business _______ almost everyone is waiting for a great chance.
A.how
B.which
C.where
D.that
简答鸦片战争的起止时间,签订的条约内容及影响。
_________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________