Only allowing one answer per login

I work at a school and I am having students vote and I wanted to limit each student to one response.  Is there a way to limit a login to a single user (without locking the device).  Some of them all vote off the same computer so I can't limit it to a single device. 

I suggest you use the Unique Question function to limit the submission per student. This function will not allow the user to submit the form if the "data" entered in the assigned question field was already submitted previously. For example, if the "student 001" submitted a form, the next user cannot use "student 001" anymore.

Please check this guide for more information: How-to-set-Form-Limits-Based-on-a-Unique-Question.

Hope that helps. If you have any questions, let us know. Thank you.