Difficult modals Tony must be sick today Tina must speak Danish It must have rained last night Tina must have won the lottery
Difficult modals Tina could find a job next week (=10% chance in the future) Tina could find all the right answers when she was in high school (=past ability) Tony could take Grammar 4 again in the fall Tony could speak English when he was 5.
Difficult modals Tony could have bought a new car, but I don’t believe it. (10 % chance in the past) Tina could have known the answer, but I don’t think so. He could have taken the test, but I don’t think so.