In a chart, what does the term 'variable' refer to?

In a chart, the term 'variable' refers to a quantity or measured value that can change or take different values in different circumstances. This concept is foundational in data analysis and visualization, as variables represent the data points being evaluated or compared in a given context. For example, in a line graph illustrating sales over time, 'sales' is a variable that varies month to month.

Understanding that a variable can reflect different values helps in interpreting charts accurately, as it indicates what is being measured and how it may change based on different factors or conditions. This flexibility is crucial for drawing insights from charts and understanding the relationships between different sets of data, making option C the correct and most relevant answer regarding the role of variables in charts.