英语语法题,只是不知道为什么这么选,所以请讲一下原因

英语语法题,只是不知道为什么这么选,所以请讲一下原因1.Jean did not have go to the concern last night because she was busy( )for her examination.A.to prepare B.to be prepared C.preparing D.being prepared2.The computer does not work well,so something ( )wrong.A.can have gone B.should have gone C.must have gone D.ought to have gone3.The concert usually takes place at the People's Square.with the audience( )on the ground.A.seating B.seated C.be seating D.to seat