How many mass extinctions have occurred throughout earth's history?

• Correct Answer: five
• three
• six
• four

Explanation: Extinction is the complete dying out of a species. Once a species goes extinct, it can never return. More than 99 percent of all the species that ever lived on Earth have gone extinct. Five mass extinctions have occurred in Earth’s history. They were caused by major geologic and climatic events. The fifth mass extinction wiped out the dinosaurs 65 million years ago.

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