Final answer:
There have been five mass extinctions in the last 500 million years, with each causing the extinction of at least 50% of the species on Earth. The correct answer is C. five; 50%.
Step-by-step explanation:
Over the past 500 million years, there have been five mass extinctions, and during these events, a significant portion of the species on Earth became extinct. The most severe of these extinctions took place about 250 million years ago, which is known as the Permian-Triassic extinction event. During this event, 57 percent of all families, 83 percent of all genera, and 96 percent of all species became extinct.
It is important to understand that mass extinctions have been significant events in the history of life on Earth. More than 50 percent of species became extinct during these events, as documented in the fossil record. Biodiversity recovery after these mass extinctions has been slow, taking up to 30 million years in some cases.
Based on the information provided, the correct answer to the student's question is C. five; 50%. This indicates that there have been five mass extinctions, and each time, at least half of the species on Earth became extinct.