into use in April 2000, the hotline was meant for residents reporting water and heating supply breakdowns.

       A．Put                     B．Putting                C．Having put           D．Being put

___ into use in April 2000, the hotline was meant for residents reporting water and heating supply breakdowns.

A. Put 　 　　　 B. Putting　　 　　

C. Having put　　　 D. Being put

 ______ into use in April 2000, the hotline was meant for residents reporting water and heating supply breakdowns.

A. Put                  B. Putting          C. Having put           D. Being put

______ into use in April 2000, the hotline was meant for residents reporting water and heating supply break downs.

1. A.
   Put
2. B.
   Putting
3. C.
   Having put
4. D.
   Being put