Modal Verbs Exercise 3

ANSWERS #9 and #11

9. We should invite Sally and her husband to come to the picnic on Saturday. We haven't seen them in weeks, and they might really enjoy a nice day at the beach.
In this sentence, "might" is preferred because "could" suggests that they have the ability to have a nice day at the beach. Most native speakers will use "might."

11. We had better call Tony to see if he's at home before we go over to his house. He might not be there and we don't want to drive all the way over there for nothing.
In this sentence, "might not" is the only correct answer. "Could not" would suggest that it is impossible that Tony is at home. "Might not" suggests that it is possible that he is there and it is possible that he is not there.

ATTENTION #13

13. You ought not worry so much. It doesn't do you any good. Either you get the job, or you don't. If you don't, just apply for another one. Eventually, you will find work.
"Ought not" is not commonly used in American English.