A、By their nerve cells. B、They blink automatically. C、By seeing the mates. D、By the gas nitric oxide. A

Can you spot the fireflies in this picture? One of the fascinating things about fireflies is their sheer mystery. We know one reason they blink on and off like they do is to attract mates. It’s all about sex.
   But how do they control the blinking? In a study published in the journal Science, researchers trace the answer to the nerve cells leading to the firefly’s lantern and the presence of an enzyme that makes the gas nitric oxide.