How do the atmospheric conditions near the beginning of precambrian time contrast with the atmospheric conditions that are present now? which organisms are largely responsible for this change?

Today, our atmosphere contains nitrogen, oxygen, argon, and carbon dioxide.

But back in the Precambrain time, it consisted only of nitrogen and carbon dioxide, lacking the oxygen.

Single celled organisms like like bacteria and viruses were abundant.

I do not know the last part of your question; I am unable to help.

Answer:

it provides an alternative energy pathway for the reaction to proceed.

explanation:

a catalyst is a substance that speeds up the rate of a chemical reaction but is not consumed during the course of the reaction.

catalysts increase the rate of reaction without being used up. they do this by lowering the activation energy needed. with a catalyst, more collisions result in a reaction, so the rate of reaction increases. different reactions need different catalysts.

a catalyst works by providing an alternative reaction pathway to the reaction product. the rate of the reaction is increased as this alternative route has a lower activation energy than the reaction route not mediated by the catalyst.

Ibelieve the answer is relative humidity  because it makes more sense that way. solar flares usually occur in space it doesn't affect the earth, well it could but it wont make a significant damage.  latitude is land it doesnt do anything. prevailing winds, i dont know the correct meaning for this but i doubt that affects the land so it has to be relative humidity.