Single Choice Field Defaults to 1st Value

I have multiple single choice fields on a form.  These fields are turned off or on if a user indicates that they have multiple people to register.  Problem is the single choice field always defaults to the first value on all of the single choice fields.  So when the calculation is performed it adds up all the first values in the single choice fields.  

Can I tell the form not to select any values in the single choice fields by default without adding a '0' value first choice?

Here's my form:

https://form.jotform.com/80626765835164

In the Advanced Properties window, you can select a blank option in the Selected By Default drop-down menu.

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