When something is impossible we use....
can't
We (can, might) speak English well.
We can speak English well.
You (must/should) come to school now.
You must come to school now.
I am feeling tired. I think I (would, have to) go to sleep now.
I am feeling tired. I think I have to go to sleep now.
Time is running out. We (must, mustn't, needn't) hurry.
Time is running out. We must hurry.
Filomena was a big winter storm. Schools (had to/couldn't close).
Philomena was a big winter storm. Schools had to close.
The volleyball team (can, could) go to the Olympics this year if they try hard.
The volleyball team can go to the Olympics this year if they try hard.
True or False? We use "can" when when an action is necessary.
True
Mary gave me a letter to send. I (must, mustn't, needn't) forget to mail it.
Mary gave me a letter to send. I mustn't forget to mail it.
"Had to" and "didn't have to" are used to express...
obligation
I (cannot, can't) read a book that long.
I can't read a book that long.
That snake bite (could be, isn't) very dangerous.
That snake bite could be very dangerous.
For Ability in the past we use...
Could/Couldn't
I think I (can, could) help you learn math if you study hard.
I think I can help you learn math if you study hard.
He will be in school for another two hours. We (must, mustn't) visit him now.
He will be in school for another two hours. We mustn't visit him now.