Final answer:
The major factors for long-lasting glacial periods are having large continental masses near the poles and oceanic circulation that is more north-south than east-west, which together affect climate and glaciation.
Step-by-step explanation:
The major factors in glacial periods lasting tens of millions of years appear to be D. Both having one or more large continental masses near the poles and oceanic circulation that is more longitudinal (north-south) than latitudinal (east-west). These factors profoundly affect Earth's climate system and are crucial in understanding past ice ages. The positioning of continental masses near the poles can facilitate the accumulation of ice because these regions receive less solar radiation. Additionally, the pattern of oceanic circulation plays a vital role in climate regulation by redistributing heat; if the circulation is more longitudinal, it can effectively transport cold water from the poles towards the equator and warm water in the opposite direction, reinforcing cooler climate conditions conducive to glaciation. Milankovich's theory further suggested that changes such as the tilt of Earth's axis affected how much sunlight reached polar regions, influencing glaciations.