Are you trying to identify your participants for grading or something similar?
If you are and are using us with a recurring group of participants (like a classroom) I always recommend using our registered participants feature. This will let you always be able to tell who responding with what.
Here’s some info on registered participation: http://www.polleverywhere.com/guide#registration
Without registering them, you can add another poll question asking for their name or email since we correlate answers from the same participant in the reports.
Would either of these work for you or are you looking for something a little different?