Researchers Who Have Studied Colour Blindness and Colour Deficiency Have

Researchers who have studied colour blindness and colour deficiency have found that:

A) colour deficiency is more frequently found in Aboriginal men than in European men.
B) colour deficiency is more frequently found in women than in men.
C) total colour blindness usually occurs when cones of the retina are absent or malfunctional.
D) total colour blindness is extremely rare in animals species.