During the pleistocene epoch, which of the following organisms went extinct according to the geological record?
a. bison
b. horses
c. mammoths
d. mastodons

Based on geological records, mammoths were organisms that went extinct during the Pleistocene Epoch. They were known to be the ancestors of Indian elephants. They were said to have lived 2 million years ago to 9,000 years ago, years after the dinosaurs went extinct. 

Mammoths are herbivorous animals with long and dense fur and underfur. They also have long tusks that they use for mating, protecting, or for digging food in the snow. The longest tusks found reached up to 13 feet or 4 meters long.