1.Mr.Smith works ____ an office.A.on B.with C.in D.to 2.People buil bridges to go _____ the big river.A.through B.cross C.to D.across 3.He swims _____ the river every week.A.under B.over C.on D.in 4.Can you come _____ 9 a.m._____Thursday?A.ai,on B.in,on C.at,in D.at,at 5.I'm afraid _____ he cannot see you now.A.and B.that C.of D.them