A lion ____ only attack a human being when it is hungry .
-- I didn't realize how popular the restaurant was until I made a reservation the other day.-- I beg your pardon, but when __________?
It_____ have been Tom that parked the car here, as he is the only one with a car.
-- Do you think it's a good idea to make friends with your students?-- ______, I do. I think it's a great idea.
Every evening after dinner, if not ______ from work, I will spend some time walking my dog.
Drink driving should be treated as a crime ________ whether the driver causes a crash.