Answer:
3 - Photoreceptors.
Explanation:
Photoreceptors are a sensor that is connected to your retina. They sense light and send the message to your brain. The sensors automatically squint your eyes if something will blind you.
The correct answer is 'photoreceptors'.
Collagen is the structural protein found in skin and connective tissue. This protein is the most abundant protein, that makes up one-third of the protein in the human body. The function of this protein in the skin is to give the skin strength and elasticity, and to replace dead skin cells. In connective tissues it s<span>upports structures and anchor cells to each other.</span>
