D
Below is a question with multiple-choice answers. Choose the correct option based on your reasoning.

### Question:
Which best describes two organ systems working together to help maintain homeostasis?

### Choices:
A. The reproductive organs produce sex cells.
B. The nerves carry signals from the eye to the brain.
C. The bones and muscles of the hand work together to grip a pencil.
D. The muscles of the chest tighten to push carbon dioxide out of the lungs.

### Answer:
