Final answer:
The symbol 'c with a line above it' relates to an average in scientific contexts but in the options given, 'c' is the correct answer representing the Celsius symbol, used to denote degrees Celsius on the temperature scale.
Step-by-step explanation:
The symbol c with a line above it usually stands for an average value in scientific notations; for example, v with a line over it stands for average velocity. However, in the options provided by your question, the correct answer is c. The Celsius symbol. The Celsius scale is widely used in science and is symbolized by °C, pronounced as "degrees Celsius." The Celsius scale measures temperature, where 0°C is the freezing point and 100°C is the boiling point of water. Other temperature scales include Fahrenheit and Kelvin, which have different points for freezing and boiling of water.