This system releases carbon dioxide gas and takes in oxygen. A: respiratory
B: ciruclatory
C: skeletal
D: digestive

a.  respiratory

Explanation:

The lungs and respiratory system allow us to breathe. They bring oxygen into our bodies (called inspiration, or inhalation) and send carbon dioxide out (called expiration, or exhalation). This exchange of oxygen and carbon dioxide is called respiration.

those sounds of the natural world are bioacoustics, and they're more than a false-color spectrogram of data from the musiamunat conservation area.

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