Which of the following describes an organism? (2 points) select one: a. a group of atoms working together b. a group of cells working together c. a group of tissues working together d. a group of organ systems working together

An organism is d. a group of organ systems working together.

An atom goes into a molecule which goes into a cell which goes into a tissue which goes into an organ which goes into an organ system which goes into an organism. 

Organs working together with other organs create a system of organs or an organ system. Something like this helps keep a human body, for example, functioning since everything relies on each other. 

Remember that if your respiratory (breathing) system and nervous (brain) system did not work together, you would not be alive, and therefore no longer a living organism.