Nitrogen is required for protein formation. What is responsible for the bulk of nitrogen fixation? A.
air

B.
animals

C.
bacteria

D.
lightning

C: Lightning

Explanation:

Because  bulk of nitrogen fixation is done by free living or symbiotic bacteria.

answer: land bridge theory. land bridge theory held that shifting portions of dry land explained the finding of identical species on different continents. plate tectonic theory eventually eliminated the land bridge theory.

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