Assertion : Primitive atmosphere was formed by the lightest atoms.
Reason : The primitive atmosphere was reducing in nature.

Options

A. If both the accertion and the reason are true and the reason is a correct explanation of the assertion
B. If both the assertion and reasone are true but the reason is not a correct explanation of the assertion
C. If the assertion is true but the reason is false
D. If both the assertion and reason are false

Answer

B

Explanation

(b) The lightest atoms of nitrogen, hydrogen, carbon etc. formed the primitive atmosphere. Hydrogen atoms were most numerous and most reactive in primitive atmosphere. First hydrogen atoms combined with all oxygen atoms to form water and leaving no free oxygen. Thus primitive atmosphere was reducing atmosphere (without free oxygen) unlike the present oxidising atmosphere (with free oxygen). Presence of huge amount of free hydrogen in primitive atmosphere also proves its reducing nature.