Which symbol commonly denotes slope and what does it represent?

• A. $k$, denoting the curvature of a line and computed as the second difference of $y$ over the change in $x$
• B. $p$, the proportion of $x$ increase to $y$ decrease described as run over rise, used to describe slope when lines run leftwards only
• C. $m$, the ratio of the vertical change to horizontal change between any two points on the line
• D. $b$, representing the steepness of a line measured as the vertical intercept value that changes proportionally with $x$ across the graph

Answer: (C)