出几个关于名词，名词所有格，冠词，代词英语题

冠词：( )walk is expected to last all day,so bring ( )packed lunch. A.A;a B.The;不填 C.The;a D.A;不填 C
代词：To save class time,our teacher has ( )students do half of the exercise in class and complete the other half for our homework. A.us B.we C.our D.ours A
名词：He and his wife are of the same ( );they both want their son to go to college. A.soul B.spirit C.heart D.mind D
名词所有格：（ ）educational system is very good. A.America B.American C.America's D.American's C