Biology CLEP Prep Practice Exam 2026 - Free Biology CLEP Practice Questions and Study Guide

The circulatory system is made up of various organs, such as the heart, blood vessels, and blood, and is responsible for transporting oxygen and needed nutrients to different parts of the body. This is essential for the proper functioning of our cells and organs. While options A, B, and C may seem related to the circulatory system, they are not its primary role and can also be performed by other systems in the body. For example, regulating blood pressure is primarily controlled by the nervous and endocrine systems, interacting with the immune system is a function of the lymphatic system, and maintaining fluid balance is mostly controlled by the urinary and integumentary systems. Therefore, the main role of the circulatory system is to transport oxygen and nutrients throughout the body.