Corn originated in the New World and thus was not known in Europe until Colum...

Corn originated in the New World and thus was not known in Europe until Columbus found it ________ in Cuba.
A.being cultivated                 B.having cultivated
C.been cultivated                         D.cultivating
3.Who would you rather _______ with you, George or me
A.going                B.to go     
C.have gone                D.went
4.Water is _______ to the growth of crops.
A.absolute         B.special      
C.moderate                 D.essential
5.You ______ all those calculations ! We have a computer to do that sort of thing.
A.needn't have done                         B.must not have done