What does a protoplanetary disk most likely have in common with Earth's Solar System? A. They both decrease in gravity as they accumulate more mass. B. They both have well-defined planets that orbit due to gravity. C. They both have planets that have formed without gravity. D. They both are in motion and are held together by gravity.

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.

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