The smog is due（ ）invisible gases，mostly from automobile exhaust.

单选题

The smog is due（ ）invisible gases，mostly from automobile exhaust.

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单选题

It is occasionally necessary to cancel the takeoff clearance due to _______ ．

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单选题

Chronic bronchitis, a more serious condition, is a constant __________ or inflammation of the lining of the bronchial tubes, often due to smoking.

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填空题

CCA101,weather information: the weather is below (　　) due to dense fog. 管制员向航空器驾驶员通报天气情报信息：由于大雾天气低于最低标准

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材料题

amounts of car exhaust fumes（汽车排放的废气）and factory pollution. Breathing problems could well increase and many non-sufferers may have difficulties for the first time.Wildlife has suffered too.In lowland forests,elephants,deer,and tigers have been driven out of their homes by smog.But smog is not just an Asian problem.In fact,the word was first used in London in 1905 to describe the mixture of smoke and thick fog.Fog often hung over the capital. Sometimes the smog was so thick and poisonous that peo

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