What plan is on the free trial?

During the 15 trial you are on the Professional plan (not the Standard or Basic).  You can change at anytime by going to the Gear > Billing and subscribing to the plan you want.  

Here is a list of the features that come with each plan.

https://surveytown.com/pricing/

If you do not subscribe before the free trial is over, you will be automatically downgraded to the Basic plan.