Which of these sentences characterizes the regulatory mechanisms of gene expressions in organisms?

According to a source the answer is B. They save energy and metabolites and help the organisms to respond to the environmental changes.

A genotype is a set of genes in the human DNA responsible for different traits. It represents your complete identity that you will inherit from your parents and ancestors.
On the other hand, a phenotype is how that trait expresses physically, a characteristic, a visible description of your physical features, including height, eye color, overall health, history of diseases, the ability to gain or lose weight fast, what type of food you like, what you enjoy and what you hate.