The circulatory system is also known as an ________ system.

The circulatory system is also known as an ________ system.

• A. Organ
• B. Nervous
• C. Endocrine
• D. Digestive

Answer: (A)

The main idea is how body organization is described: an organ system is a group of organs that work together to perform a common function. The circulatory system fits this because it’s made up of the heart and a network of blood vessels (and the blood itself) that together transport blood, nutrients, gases, and wastes throughout the body. Saying it’s an organ system distinguishes it from naming a single organ or from other systems like the nervous, endocrine, or digestive systems. So the word that completes the sentence is organ, giving “an organ system.”

The main idea is how body organization is described: an organ system is a group of organs that work together to perform a common function. The circulatory system fits this because it’s made up of the heart and a network of blood vessels (and the blood itself) that together transport blood, nutrients, gases, and wastes throughout the body. Saying it’s an organ system distinguishes it from naming a single organ or from other systems like the nervous, endocrine, or digestive systems. So the word that completes the sentence is organ, giving “an organ system.”