1.sofast__thatitisdifficultforustoimagineitsspeed.
A.travelsthelight
B.doesthelighttravel
2.__fortheleadershipoftheparty.weshouldnothavesucceed
A.hadnotitbeen
B.haditnotbeen
3.__noairorwater,therewouldbenolife.
A.werethere
B.isthere
4.Theoldcouplehavebeenmarriedfor40yearsandneveronce__
witheachother.
A.havetheyquarreled
B.hadtheyquarreled
希望知道的人可以帮助我一下,