The Eda Gene, Which Regulates Growth of Lateral Armor Plates

The Eda gene, which regulates growth of lateral armor plates in stickleback fishes,

A) codes for more armored plates in the recessive allele than the wild type.
B) is hard to study because the recessive condition affects surrounding tissue.
C) has variants responsible for much of the variation in the number of lateral plates each stickleback grows.
D) is easy to study because the recessive condition affects surrounding tissue.