几道初中英语题,解答请简单的说明下理由

几道初中英语题,解答请简单的说明下理由
1.The light is on in his home. He( )back
A.will be B. must be C. won't be
2.Must I copy all the words now? -- NO,you( )
A.can't have to B. mustn't C. needn't
3.---Mary studies very hard
---( )
A. so do you B. so you do C. you do so
4. In this age,information( )from all corners of the earth.
A.coming B.have come C.comes