Mr. Jenkin regretted ______ his secretary for the mistake, for he later discovered it was his own fault.
Harry is feeling uncomfortable. He __________ too much at the party last night.
When I was a child, I __________ watch TV whenever I wanted to.
Since nobody gave him any help, he __________ have done the research on his own.
The children __________ lost in the woods; otherwise, they would have been at the lakeside camp as scheduled.
-Where did you get this book?-I picked it up from a second-hand bookshop if you __________ know.