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1) Nitrogen is obtained from the fractional distillation of liquefied air at about a. 196°C b. 186°C c. 176°C d. 166°C
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2) A greenhouse gas that absorbs energy and maintains the earth's temperature is a. carbon dioxide b. oxygen c. nitrogen d. argon
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3) The main constituent in air is a. nitrogen b. oxygen c. argon d. water vapor
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4) On cooling, a liquid will be changed into a. dense b. solid c. semi-solid d. liquid
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5) Combustion cannot take place without a. water b. carbon c. air d. zinc
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6) Breathing is a process that refers to the inhaling and exhaling of a. gas b. air c. molecule d. proton
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7) Greenhouse gases and other harmful gases are bringing huge damage to the atmosphere like a. acid rain b. global warming c. ozone hole d. all of them
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8) The process of burning under the presence of oxygen is known as a. combustion b. reaction c. respiration d. production
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9) In desert areas, the water vapor content is a. different b. higher c. low d. constant
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10) To perform fractional distillation of air, it must be liquefied and then purified to remove a. dust b. molecule c. atom d. rust
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