How can I show Sub-Categories corresponding to the Category of the answer (using widget)?

Hi everybody,

let’s figure we have 2 Categories (Dogs and Cats) and each Category has Sub-Categories (Food for Dogs, Sport for Dogs and Food for Cats and Sport for Cats)…

Now, I want to show ONLY Sub-Categories ‘Food for Dogs’ and ‘Sport for Dogs’ when user is in Category page ‘Dogs’ or when he is reading a Question or Answer in ‘Dogs’ category. Same for ‘Cats’…

How?

I try with Widget Logic but cannot understand the right syntax of rule I have to add… : /

Any other option?

Thank you