The system is a network of nerve cells and fibers that transmit nerve impulses throughout the body.

a. Respiratory
b. Circulatory
c. Nervous
d. Endocrine

c. Nervous

To determine the correct answer, we can break down the options and their descriptions:

a. Respiratory: This option refers to the system responsible for respiration and the exchange of gases, including oxygen and carbon dioxide, in the body.

b. Circulatory: This option pertains to the system responsible for the circulation of blood, nutrients, oxygen, and waste products throughout the body.

c. Nervous: This option aligns with the description provided in the question. The nervous system comprises a network of nerve cells (neurons) and fibers that transmit nerve impulses, allowing for communication and coordination between different parts of the body.

d. Endocrine: This option refers to the system responsible for the secretion of hormones that regulate various bodily functions and processes.

Based on the given description, the correct answer is c. Nervous, as it specifically mentions the transmission of nerve impulses throughout the body.