B is the compound because a compound is two or more different atoms that combine.
Explanation:
The first option, the others are normal
Thunder is caused by the extremely rapid expansion of air around a bolt of lightning due to the very high temperature. It is also caused by the change of pressure around a lightning bolt.
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<span>Chemical properties, such as density, must be observed when a substance is in its natural state at room temperature and normal atmospheric pressure.</span>
<span>Many of the sensory and motor functions are controlled by the central nervous system and the brain. An example of this would be grabbing a hot pot from the stove. Your brain sends a signal to your hand to tell it to grab the pot. When you grab it your sensory nerves detect that the pot is hot and is burning your hand. The signal it sends back to the brain is one that there is pain and to release the pot.</span>