Form field select customization - how to require user to make a dropdown selection?

Site URL: https://grtv1.squarespace.com/

Hi everyone,

I was wondering if anyone could help with some custom CSS (or any other more obvious solution that I have missed) where a website user filling out a form is required to make a selection from a dropdown. Yes, I know about the form field settings and I have certain fields toggled to "required".... however, the SS form just shows up with the first option in the select list already selected. So basically, a user could breeze through the form without actually making intentional selections, and just submit what is there by default. 

In the dropdown fields for Purchaser type, Contact Preference, Desired Suite type, and Where did you hear about us?, I would like for those fields to be empty, or unselected, as a default, rather than showing the first option in the list. 

I hope I'm explaining my question clearly. Screenshot below. And the site is at:

https://grtv1.squarespace.com/

PW is GRT

This worked! Thanks so much Paul!