The correct option is
C Both B and C
Frog eyes have eyelids, as upper and lower one. The upper eyelid, here, is a simple skin fold. The lower one is a translucent membrane. When a frog's eyeball is retracted into the eye socket the lower lid spreads over its surface. It is immovable, small and semitransparent.
So, the correct answer is 'Both B and C'.