—How was the professor's lecture?—Impressive. Thank you so much for giving me a lift during the rush hours. If not, I ________ the lecture today.

They        have arrived at lunchtime, but their flight was delayed.

If it 　　for your help,we would be in serious trouble.

The safety belt saved the boy; otherwise, he _____ in the accident.

We        have bought so much food now that Suzie won’t be with us for dinner.