Avoid 'Resume' or 'Restrict' or 'Save and Continue' options when ever possible.
Most survey packages have options which allow users to resume a survey, or attempt to restrict participants to only one attempt. THESE SHOULD ALWAYS BE AVOIDED! This cannot be stressed enough.
These have the potential for exposing data to other participants. For example if you had a survey which both partners of a relationship were required to do a survey potentially they will use the same computer and as such the second participant could see a half completed survey from the first participant.
Only use this is you are 100% sure that two or more participants will not be using the same computer, EVER!