Which of the following gases is normally not present in air?

问题描述:

Which of the following gases is normally not present in air?
A.Oxygen B.Hydrogen
C.Nitrogen D.Carbon Dioxide
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To myth2000:Sorry but one answer is too little for me..lets wait for another answer.

BNormally,the air is combined by 20.25% Oxygen(A),78% Nitrogen (B),0.03% Carbon Dioxide (D) and some other rare gases.Anyway Hydrogen (B) is also one of the components of air,but the content is very v...