Make Readonly items

Bonjour à tout le monde
I want to make certain modality read-only if a modality is chosen (YES)

I6.What are the main educational activities that Manel has practiced since the educational structures were closed during the 2019/2020 school year?

I want if the “Pas d’activité” modality is YES that all the other modalities are read only

thank you

Wrong design. You ask this kind of question if you expect answer to every bullet.
If the question may be inapplicable, do the screening first.
Q1. Were there any activities? (single-select Yes/No)
Q2. If Q1=YES, what were the main activities? (multiselect without the NONE option)