My pen friend and I keep in touch ________ sending e-mails often．

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

My pen friend and I keep in touch ________ sending e-mails often．

A．with　　　 　　 B．by 　　　　 C．on　　　 　 D．of

My pen friend and I keep in touch ________ sending e-mails often．

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

My pen friend and I keep in touch ________ sending e-mails often．

My pen friend and I keep in touch ________ sending e-mails often．

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