Question

saving sea turtles
small - scale fishing performed with nets is one of the most common fishing methods used around the world. one of the unfortunate side effects of this method is that sea turtles, which are considered threatened, get caught in the nets along with the fish. conservation biologists at the university of exeter in england recently devised a way to prevent these sea turtle deaths, which they tested at a fishery in northern peru. they found that attaching green led lights to the nets warned the turtles away, possibly because the lights made the nets more visible. the number of sea turtle deaths was reduced, but the number of fish caught seemed to remain the same.
what is the main, or central, idea of the passage?
one problem with small - catch fishing is that sea turtles get caught along with fish.
conservation biologists are researching ways to save the threatened sea turtle population.
to prevent turtles from becoming caught in fishing nets, conservation biologists attached led lights to the nets.

Explanation:

The passage first presents the problem of sea turtles getting caught in fishing nets during small - scale fishing. Then it focuses on the solution devised by conservation biologists: attaching green LED lights to nets to prevent sea turtle deaths, with the result that turtle deaths reduced while fish catch remained similar. The first option only states the problem, the second is too general about biologists' research. The third option accurately captures the main action (attaching LED lights) and its purpose (prevent turtles from being caught) which is the central idea.

Answer:

To prevent turtles from becoming caught in fishing nets, conservation biologists attached LED lights to the nets.