Question

read the passage.
making towers bird - friendly
the lights on tall communication towers warn pilots to avoid the towers when flying at night. unfortunately, the steady red lights often used on towers have the opposite effect on birds: the bright beams attract and confuse them. instead of avoiding the lights, the birds fly directly toward them, crashing into the towers or becoming entangled in power lines. millions of birds have died this way. however, there is a solution. unlike steady lights, flashing or blinking lights dont attract birds. in response to demands from conservation groups, the federal aviation administration in 2016 began requiring communication towers in the u.s. to use blinking lights instead of steady ones.
what is the main, or central, idea of the passage?
to save birds, communication towers have begun using blinking lights.
birds are attracted to the steady red lights on communication towers.

Explanation:

The passage first explains that steady red lights on communication towers harm birds by attracting and confusing them, leading to millions of bird deaths. Then it introduces the solution: blinking lights don't attract birds, and in 2016, the FAA required U.S. communication towers to use blinking lights to save birds. The first option captures the main idea of the problem (harm from steady lights) and the solution (using blinking lights to save birds). The second option only focuses on the problem part, not the solution which is a key part of the passage's main idea.

Answer:

To save birds, communication towers have begun using blinking lights.