Check box selection used to 'disable' or hide form fields

I have a simple 1 page form, composed on many fields, organized into sections.

At the top of the form are two (2) check boxes. Let's call them check box "A" and "B"

Objective:

If "A" is selected, fields in all three sections are visible and available.

If "B" is selected, only fields in Sections 1 and 3 are available.

Solution:

I'm indifferent to the type of solution proposed. Also, I do not have a preference for how exactly the fields are disabled or obscured. The goal is to send the user a visual sign that they should not complete the fields.

Thank you very much!