I .........work late tomorrow.We are very busy at the office.(have to, must)
The drivers ..........stop before they crashed into each other.(could, were able to)
You....get in without a ticket. Not a chance. ( may not, cannot)
You.....forget to type this letter.It is very important. (needn't, mustn't)
I think you.......try to relax more. (should, could)
You ......always wear a hat when you go out in strong sunlight.(have to, must)
David .......work as a taxi driver. He can't drive. ( might not,couldn't)