Read the passage North American river otters are a species whose population can indicate the degree of health in the surrounding environment. The
otters experienced a sharp decrease in numbers in the 1900s. This was due to fur trapping and pollution. They are not considered
endangered today, though.
Which sentence could be added to the passage to maintain its formal style?
1.Fur trapping and pollution are legal today
2.The otter is on the endangered species list
3.Through conservation efforts, the otter population has recovered.
4.If people would leave otters alone, they would be healthy