Many clothing manufacturers now substitute artificial silk _____ natural silk to cut down costs of production．

Many clothing manufacturers now substitute artificial silk _____ natural silk to cut down costs of production．

1. A.
   with
2. B.
   by
3. C.
   for
4. D.
   of

Many clothing manufacturers now substitute artificial silk _____ natural silk to cut down costs of production．

     A．with           B．by        C．for       D．of

Many clothing manufacturers now substitute artificial silk _____ natural silk to cut down costs of production．