Your ability to perceive the color of a vibrant blue sky or a red rose depends on the responses of the in your retina, and your ability to find your way to the bathroom in the dark depends upon the in your retina. A. cones; blind spots
B. hair cells; rods
C. rods; cones
D. cones; rods

this is true, assuming that the allele is completely recessive and incomplete dominance is not a factor.

the correct answer is: b. pantala flavescens, because these organisms would have a high level of genetic variation due to sexual reproduction.  

because involves two organisms (parents) whose genetic material combines, sexual reproduction leads to genetic variation in new generations of offspring. the offspring is an unique organism, with new genome, more protected with the higher ability to adapted. this process is fundamental to evolution.

not necessarily. higher fitness requires the organism to be reproductive successful. for example, an organism at age 10 with 15 offspring is much more fit than an organism at age 15 with only 5 offspring.