On a karyotype, which pair(s) of chromosomes are always the sex chromosomes (no matter what the organism is)? A. the 23rd pair B. the last pair C. the first pair D. all of them

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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