users/ messages/ information/ send/ receive/ without/ computers/ can/ through/ telephone lines/ leave/ their.

• A. 
  Without leaving their computer, users can send messages and receive information through telephone lines.
• B. 
  Users leave their computer to send messages and receive information through telephone lines.
• C. 
  Through telephone lines, users can send messages and receive information by leaving their computer.
• D. 
  Without telephone lines, users can send messages and receive information by their computer.