The highest and lowest values of a weather element observed over the entire period of record are

The correct answer is: C. absolute extremes.

Absolute extremes are the highest and lowest values of a weather element observed over the entire period of record. They are also known as record highs and record lows. Absolute extremes can be used to track changes in climate over time. For example, if the average temperature in a city has been increasing over the past few decades, we might expect the absolute high temperature to also increase.

Here is a brief explanation of each option:

• A. extremes: This is a very broad term that could refer to any extreme weather event, such as a hurricane or a tornado. It is not specific to the highest and lowest values of a weather element.
• B. average extremes: This term is not commonly used in meteorology. It could be interpreted to mean the average of the highest and lowest values of a weather element, but this is not a standard way of calculating extremes.
• D. relative extremes: This term is also not commonly used in meteorology. It could be interpreted to mean the highest and lowest values of a weather element relative to some other value, such as the average value. However, this is not a standard way of calculating extremes.