Select from the following.
(1). layers of fat
(2). electricity
(3). food
(4). focusing a lens
(5). shadows
(6). dolphins
(7). Light bulbs
(8). pets
Q: You are presented with the quiz "What helps humans see?" But you don't know the answer, so you turn to your teacher to ask for hints. He says that "alight bulb is used for seeing in the dark" and "humans are unable to see clearly in the dark". So, what's the best answer to the question?
A:
(7).