Some can never go above 4000 meters, because their body is unable to ___________ these extreme conditions.
Do you think it necessary that we have all the chairs_________?
________do you think _________ the monitor of our class?
.We were about to go downstairs when the lights_________.
.Jack couldn’t answer the question_________ got the money.
—You did so much work today.You must be very tired. —No,I’m not_________tired.