Scientists believe that some mass extinction events are possibly caused by asteroids, volcanic activity, or climate change. How many mass extinctions have occurred on Earth in the last 4.6 billion years?

Earth has experienced five major mass extinction events during the last 4.6 billion years. These are often called the “Big Five” and include events caused by factors such as climate change, volcanic activity, and possibly asteroid impacts. Therefore, the correct choice is five.

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