Are there any best practices for adding "(s)" to a label on a field that can have more than 1 option selected?
I think it looks cleaner without the "(s)", but having the "(s)" seems to help with usability.
My rule of thumb...
For fields that allow ONLY ONE selection:
For fields that allow MORE THAN ONE selection:
The question is really asking for all of the answers to the question, even if the number of answers turns out being 1... the query was still for all (plural). This follows in line with how you'd ask the question in plain English. For example, if it were a verbal question you'd likely ask...
Which students are in your class?