①______theearthtobeflat,manyfearedthatColumbuswouldfallofftheedgeoftheearth.(1996.6)
A.HavingbelievedB.BelievingC.BelievedD.BeingBelieved
②_______ateacherinauniversity,itisnecessarytohaveatleastamaster'sdegree.(1995.1)
A.TobecomeB.BecomeC.OnebecomesD.Onbecoming
③Realizingthathehadn'tenoughmoneyand____toborrowfromhisfather,hedecidedtosellhiswatch.(1995.1)
A.notwantedB.notowantC.notwantingD.wantingnot
④___itornot,hisdiscoveryhascreatedastirinscientificcircles.(1997.1)
A.BelieveB.TobelieveC.BelievingD.Believed