Had he not come an hour earlier, he___the secret that his mother was always there.
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.
Don't be angry with us. We __________ with you together, but we were busy with our final reports when you called in.
-__________ I turn on the TV for you, Grandpa? -Yes, thanks a lot, my dear. You're so considerate.