What does the term "Coefficient of Expansion" refer to?

The term "Coefficient of Expansion" refers to the measurement of how much a material expands when its temperature increases. Specifically, it quantifies the unit increase in length of a material for each degree of increase in temperature, making option C the correct choice. This property is crucial in plumbing design and engineering because materials used in piping systems respond to temperature changes, which can lead to expansion or contraction. Understanding the coefficient helps designers predict how materials behave under varying thermal conditions, ensuring that systems are designed to accommodate these physical changes without causing damage or stress on the components.

This concept is vital for ensuring longevity and functionality in plumbing systems, where temperature fluctuations are common. The other options do not accurately reflect the definition of the coefficient of expansion; they either misrepresent the concept or address unrelated physical properties.