Answer:
Apart from the bottom lid and upper lid fogs have a third eyelid which is known as the nictiating membrane which is a semi-transparent membrane.
This membrane helps the frog to cover their eye when they are underwater so that the eye gets protected from dust or mud and it also helps frog to see underwater so that they can get a protected place.
So this nictiating membrane helps frogs to get protection from their predators by hiding underwater therefore it helped frog in their survival. Nictiating membrane also helps in remaining the frog eyes moist during hot days.