Biology CLEP Prep 2025 – 400 Free Practice Questions to Pass the Exam

Muscular is not considered a vital organ system because it is composed of voluntary and involuntary muscles that serve as the movement and support mechanism for the body, rather than being a crucial part of a regulatory system for bodily functions. The other options (A, B, D) all refer to organ systems that are essential for the body to function properly. For example, respiratory system is responsible for gas exchange, gastrointestinal system for digestion, and excretory system for elimination of waste products. While the muscular system does play a role in supporting these functions, it is not considered a vital organ system on its own. Therefore, option C is the correct answer.