The fastest growth rate for a species occurs at temperatures where a cell's work most efficiently.
a. nucleic acids
b. lipids
c. polysaccharides
d. proteins
e. membranes

Proteins

Explanation:

Carbohydrates, proteins, nucleic acids, and lipids are the macromolecules present in the cells and perform specific functions. Among these macromolecules, proteins are responsible for growth and development. Proteins make the muscle mass of the body. Enzymes are proteins with catalytic power. Enzymes serve to speed up the anabolic and catabolic reactions occurring inside the cells.

The anabolic reactions make complex molecules (carbohydrates, proteins, nucleic acids, and lipids) from simpler substances and these complex molecules are used by cells for growth and development. For example, protein synthesis by joining the amino acids together is an enzyme-catalyzed anabolic pathway. The newly formed proteins are used for the growth of the organisms.

Since enzymes function only under the optimum temperature conditions, each species exhibits its maximum growth at specific temperature range.