Answer the following question given this paragraph: 

Organs may be organized into organ systems. An organ system is a group of organs that work together to do the same job. For example, the heart is part of the cardiovascular system. This system also includes blood vessels and blood. The job of the cardiovascular system is to transport substances in blood to and from cells throughout the body.


Q: What is a group of organs that work together to do the same job?

 Choices:

- an organ colony

- an organ assembly

- an organ battery

- an organ system

A:
an organ system
