Ultra Violet rays or UV's cause the skin to burn in the sun.
The correct answer is Focuses energy. Eustress is defined as being beneficial to the one experiencing it. Such as being stressed out because your school final for a class is due soon, and you need to continue to work on it in order to pass.
All muscle cells share four main properties that distinguish them from other cells. These are Excitability, Contractility, Extensibility and Elasticity.
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