Modal Verbs Test - English Grammar Test - Lingportal 

Glad you like it! Would you like to pass other tests? They're helpful too. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-cB9c-3xFfvM.html

Dear nguyen su, Thank you for comment. "Could" is used as a more polite form of "can" when asking someone to provide something or do something (request). cambridge.dictionare When we apply to unknown person with request it worth to use the polite form "could".

We use might most often to refer to weak possibility. dictionary.cambridge.org/grammar/british-grammar/might

Great!