Define Nicotine...
And how it affects the body.

Nicotine is a toxic colorless or yellowish oily liquid that is the chief active constituent of tobacco. It acts as a stimulant in small doses, but in larger amounts blocks the action of autonomic nerve and skeletal muscle cells. Nicotine is also used in insecticides. It effects the body because there is an immediate release of glucose, as well as an increase in heart rate, breathing activity, and blood pressure. Nicotine also makes the pancreas produce less insulin, causing a slight increase in blood sugar or glucose

Explanation:

the plates spread at mid-ocean ridges (they are divergent plate boundaries) which allows magma to rise through the weakness between the plates. the magma then emerges as lava from the boundary and cools, creating a new crust.

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