The end of the paleozoic era was signaled by

Mass extinction of land and water animals

Paleozoic era lasted for millions of years ago. It is divided in 6 different periods. It also signal various events in evolution which include the development of most invertebrate groups. Fish and fish like vertebrates arose from the early Paleoozoic and comprise more than 50 percent of the diversity of vertebrates that inhabits today. This period ended when the mass extinction of animals occured.

The answer is c establishing proper sleep hygiene

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.