English Grammar in Use Fifth Edition

Additional exercises
4 
We have plenty of time.  We 
 yet.
 A
 mustn’t go        
B
 don’t have to go        
C
 don’t need to go
5 
I didn’t go out yesterday.  I 
 with my friends, but I didn’t feel like it.
 A
 could go        
B
 could have gone        
C
 must have gone
6 
I looked everywhere for Helen, but I 
 her.
 A
 couldn’t find        
B
 couldn’t have found        
C
 wasn’t able to find
7 
‘What do you think of my theory?’  ‘You 
 right, but I’m not sure.’
 A
 could be        
B
 must be        
C
 might be
8 
Our flight was delayed.  We 
 for two hours.
 A
 must wait        
B
 must have waited        
C
 had to wait
9 
I’m not sure whether I’ll be free on Saturday.  I 
 .
 A
 must have to work        
B 
may have to work        
C 
might have to work
10 
At first they didn’t believe me when I told them what had happened, but in the end
 I 
 them that I was telling the truth.
 
A 
was able to convince        
B
 managed to convince        
C
 could convince
11 
I promised I’d call Amy this evening.  I