One should opt optionals by the following strategy:

1. Subjects in which you have interest or in which you holds expertise (including your degree).

2. Try to opt those subjects which are scoring. It's an undeniable fact that there are some subjects which are scoring.

3. Some subjects are least chosen one, they will give you better marks as they have less competition than the most selected ones (select them if you can cover them, otherwise, don't).

4. As you are going to appear in 2022, so analyse the subjects which you can handle and once you select any subject try to learn their jargons, relative vocabulary and basic knowledge.

Hope this helps.