The muscles of the heart are constructed out of:

A) nucleotides
B) complex carbohydrates
C) cholesterol
D) proteins

Thank you.

The muscles of the heart are constructed out of proteins. To arrive at this answer, you can recall some basic knowledge about the composition of muscles and then apply it to the specific case of the heart.

Muscles, in general, are made up of proteins. Proteins are essential for the structure, function, and movement of muscles. They are composed of amino acids, which are the building blocks of proteins.

The heart, being a muscular organ, follows the same principle. The contraction and relaxation of the heart muscles are responsible for pumping blood throughout the body. Therefore, it requires a considerable amount of proteins for its structure and function.

Hence, the correct answer is D) proteins.