A. They are found under the oceans. B. They were most active when the Earth was first formed. C. Their emissions created Earth’s atmosphere. D. Their fumes are mostly steam.
A. Training astronauts to adapt to the extreme space. B. Helping astronauts work in the extremes of space. C. Designing the special clothes to protect astronauts. D. Finding the suitable clothing material for astronauts.
A. It can cause severe burns. B. It can freeze skin in a short time. C. It can expand the gases in the body. D. It can cause severe pains in the body.
A. He was a well-known American astronaut. B. He designed devices to protect pilots. C. He designed the first anti-pressure aircraft. D. He became successful for his flying skills.
A. useful B. available C. feasible D. desirable
A. closing，trembling B. closed，trembling C. closed，trembled D. closing，trembled
A. was B. being C. turned D. got
A. they had got to the bus stop B. they got to the bus stop C. did they got to the bus stop D. had they got to the bus stop
A. replace B. reduce C. exchange D. trade
A. excess B. process C. access D. assess
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