Either the boy or his sister must have dinner here.
It is the first time that Martin has been to the South Pole, ________?
If it _____ for the heavy rain then, we would have arrived here ahead of time.
We should protect the environment, for plenty of fresh air ________ to good health.
By the time you arrive home, I ____ ,so please don’t make any noise when you come in. A.have been sleeping B.would have slept C.had sleptD shall be sleeping
-----What upsets him? -----_____ his computer is out of order.