Answer to Question 1
A, B, C
Color vision is the ability to detect color. Color blindness may be genetically inherited, is usually seen in males, or may result from macular degeneration or other disease that affect the cones of the eye. The cones of the eye are part of the retina and are unrelated to the lens of the eye.
Answer to Question 2
A
Inadequate dietary intake or metabolic changes can cause the nails to become brittle. As a person ages, nails thicken, become ridged, and may yellow or become concave in shape. Brown or black discoloration of the nail plate may indicate a fungal infection. Bluish-gray discoloration of the nail plate signals excessive intake of silver salts.