What happens when the diaphragm contracts?
a. the rib cage moves down.
b. the volume of the thoracic cavity increases.
c. the diaphragm rises.
d. the volume of the thoracic cavity decreases.

The volume of the thoracic cavity decrease.

Explanation:

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what do the different brain waves do?

explanation:

brainwaves are produced by synchronised electrical pulses from masses of neurons communicating with each other. brainwaves are detected using sensors placed on the scalp. brainwave speed is measured in hertz (cycles per second) and they are divided into bands delineating slow, moderate, and fast waves.

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d.  

there was a variety of food available on island x, but there were only large seeds and nuts on island y.