Most plants and all animals depend on to meet their need for nitrogen.
lightning strikes
denitrifying bacteria
bacteria that break apart cellulose
nitrogen-fixing bacteria

nitrogen fixing bacteria

Explanation:

Most plants and animals are dependent on nitrogen fixing bacteria for their nitrogen requirements. As they are incapable of absorbing the atmospheric nitrogen directly. The soil bacteria traps the atmospheric nitrogen convert it into forms like ammonia, nitrates and nitrites which are readily absorbed by the plants and some soil borne animals.

a. energy is absorbed in the reaction.

if in a given reaction the energy of products is greater than the energy of reactants it means that reaction is endothermic and during the reaction, the energy is absorbed by reactants. in an endothermic reaction, the products have more stored chemical energy than the reactants. and in this reaction the reactants are more stable than products before the compounds with less energy are always more stable.

50.23 i believe is correct but don't quote me on that.