hair, nail, eye

hair
My answer : Slight strings from head. It protect head from sun or impact
Dictionary : the thin, thread-like parts that grow on your head

nail
M : Hard part at the end of fingers and toes
D : the hard surface at the end of your fingers and toes

eye
M : Parts of face. Generally we have two of them.We can see things with them
D: one of the two organs in your face, which you use to see with