Read the passage: In the 1800s, sea otters were hunted for their fur. The fur trade between North America and Europe was booming, and sea otter fur was a popular option because of its thickness. By the mid-20th century, sea otters had been hunted to near extinction. Only 1,000–2,000 sea otters were believed to be living in the wild in 1929. Many people thought the species would soon become extinct. However, due to conservation efforts during the second half of the 20th century, sea otter populations recovered. The strengthening of the number of sea otters in the wild is often considered to be one of the greatest successes in marine conservation

What point does the author make in the passage?

Conservation efforts have successfully increased sea otter populations.
Hunting for sea otters was a sport in the 1800s.
Sea otter fur is popular because it is very warm.
The fur trade started the problem of sea otters being endangered.