56、Is oxygen the only gas     helps fire burn?

              A．that                B．/                     C．which             D．what

      57、The first place   we visited in that city was a big factory.

              A．where             B．in which         C．that                D．which

      58、Which is the largest bridge    was built across the river?

              A．that                B．which             C．where             D．on which

      59、Please pass me the dictionary   cover is black.

              A．which             B．its                  C．whose             D．which of

             60、    is natural, she goes abroad with her husband.

              A．It                  B．What              C．Which            D．As

56、A  57、C  58、A  59、C  60、D