"select" field type question for marketo forms: can the 1st option be given an input value?

Hello,

I did some checks in the community and was not able to find anything for this particular case ... Please add any addnl resources if I am posting something that has already been solved.

We'd like to implement a 2 item drop down menu that defaults to Yes in our marketo forms. We are hoping to continue using the boolean field we've been using in the backend. I've thought the boolean backend may have been the issue but it looks like trying other field types such as string to string still forces a first label value with no input value allowed. I understand the utility of that first select item (forces someone to select an option, and ensures you don't allow a value to be submitted if they simply skipped over the field), but my question is if the above is possible and if there are additional things I need to build outside of the forms to enable this functionality?

Thanks for everybody's time.