The correct answer is: A. Pleistocene or ice age.
The Pleistocene epoch is the geological epoch that lasted from about 2,588,000 to 11,700 years ago, spanning the world’s most recent period of repeated glaciations. The end of the Pleistocene corresponds with the end of the last glacial period and the beginning of the Holocene epoch. The Pleistocene is divided into the Gelasian, Calabrian, Ionian, and Tarantian stages.
The Pleistocene epoch is sometimes referred to as the Ice Age, although this term can also refer to the entire Quaternary period, which includes the Pleistocene and Holocene epochs. The Pleistocene was a time of great climatic change, with alternating periods of glaciation and interglacial periods. The glaciers during the Pleistocene epoch covered much of the Northern Hemisphere, including North America, Europe, and Asia. The glaciers reached their maximum extent during the Last Glacial Maximum, which occurred about 20,000 years ago.
The Pleistocene epoch was also a time of great biological change. Many species of animals became extinct during the Pleistocene, including the woolly mammoth, the saber-toothed cat, and the giant sloth. These extinctions are thought to have been caused by a combination of factors, including climate change, hunting by humans, and competition from other species.
The Pleistocene epoch ended about 11,700 years ago with the beginning of the Holocene epoch. The Holocene is the current geological epoch, and it is characterized by a relatively stable climate. The Holocene is also the time period in which humans have had the most significant impact on the environment.