Drop down question type not working

I'm trying to use the new drop-down feature for some survey questions, but the survey won't activate the 'continue' button even when an option is selected (see screenshot I've attached). My code looks like the below (with the different options listed underneath). Is there something else I need to do to get this to work?

l: education
t: drop
q: What is your highest level of education?
- ...

Thanks!