Forms 3bd. The verb 'can'

For practicing:
https://www.englisch-hilfen.de/en/exercises/modals/can2.htm;
https://learnenglishkids.britishcouncil.org/grammar-practice/modals-can-and-cant;
https://agendaweb.org/exercises/verbs/can/affirmative-negative;
https://agendaweb.org/exercises/verbs/can/can-cant-test-1;
https://agendaweb.org/exercises/verbs/can/present.htm.