Q5. How to make another field become NA when I select "NO" in this field?

For example, I have total 4 fields, they are A, B, C and D.

1. Field A is a dropdown choice box with selection "Yes", "No", and "NA".

2. Field B is a dropdown choice box with selection "NA", "Eat now" and "Eat Later"

3. Field C is a dropdown choice box with selection "NA", "Eat now" and "Eat Later"

4. Field D is a dropdown choice box with selection "NA", "Eat now" and "Eat Later"

I want the field B ,C and D automatically become "NA" selection and not editable when the field A not selecting "Yes".

This request can be done by inserting the code with Javascript in the HTML form:

The results will be like:

When select YES, other 3 fields are able to edit.

When select NO or NA, the other 3 fields will become NA and cannot edit anymore.