Yes, there is a setting in the multiple choice field in the Form Builder, that you can select, which offers an option to be able to add new answers in the list when you're completing a new form. You can also select whether to save that new item in the list for use again or not.
Go to Forms > Existing Templates > edit arrow for the template > Form Builder > select the multiple choice field.
In the Field Settings on the right of the Form Builder, there will be two options that you can select / deselect.
Allow Other will create an option to add a different answer to the ones that are already listed in the multiple choice field.
Save Other will save the new answer so that it will be added to the multiple choice list and will carry across to other new forms that are created with this template after the one with the new answer has been submitted.
Once done, you will see an extra field where you can add new answers to the multiple choices:
