Choice A is the correct answer. Interpret the linear model.

1. Model: $y = mx + b$ form.
2. Slope ($m$): The coefficient of the variable ($0.5$). It represents the rate of change.
3. Context: Cost per mile.

💡 Strategic Tip: Slope is always a "rate" (something per something). Intercept is the "starting amount".

Choice B is incorrect because 10 is the y-intercept (base fee). Choice C is incorrect because$C$ is the dependent variable. Choice D is incorrect because$m$ is the independent variable.