英语选择.
1.I____giveyouananswertomorrow,Ipromise!
A.mustB.willC.mayD.shall
2.---Theyhavenotfinishtheworkuptonow.
---Well,they___.
A.shouldhaveB.shouldC.oughttoD.oughttohave
3.___youbehappy!
A.mayB.canC.mustD.would
请简要地说明原因(最好详细)