The principle underlying how salmon were genetically engineered to grow faster is a) removal of a gene responsible for feeling full after eating. b) replacement of inducible to constitutive hormone production. c) resistance to bacterial infections which waste metabolic energy in the salmon to fight off. d) addition of genes to enhance blood circulation and tissue development.

option B - replacement of inducible to constitutive hormone production.

Explanation:

During Inducible hormone production, the hormones secreted are highly regulated; however, during constitutive hormone production there is direct secretion/release of synthesized hormones from secretory vesicles to the target organs.

Hence, genetically engineered Salmons have their growth hormone on active secretion REGARDLESS of seasons, thus their growth is faster and all-year round.

b.