16、The balls are solid,     makes them very heavy.

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

      17、Is this calculator      you borrowed from Jane?

              A．which             B．one                 C．the one          D．what

       18、The scientist and his achievements   you told me about are admired by us.

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

       19、I suppose the theory he stuck     correct.

              A．to prove                B．to proving       C．to proved               D．prove

      20、He is working hard,    will make him pass the final exam.

              A．who                B．that                C．which             D．it

16、C  17、C  18、B
 19、C  20、C