1. Difficult modals Tony must be sick today Tina must speak Danish
It must have rained last night
Tina must have won the lottery

2. 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.

3. 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.