Final answer:
The answer is C) Cenozoic.
Step-by-step explanation:
The answer to your question is C) Cenozoic.
During the Cenozoic era, specifically about 50,000-10,000 years before the present, humans were able to migrate from Siberia to Alaska by crossing over the Bering land bridge. This land bridge was revealed by dropping sea levels as massive glaciers formed, creating a pathway for humans to move between the continents. Several distinct migrations occurred during this time, as humans followed the megafauna of the Pleistocene, such as mammoths and mastodons. These migrations, prompted by lowered sea levels due to massive glaciation, saw peoples moving from Siberia into Alaska. This period was marked by the pursuit of megafauna and was a crucial time in human migration and the peopling of the Americas.