Choice A is the correct answer. Interpret the y-intercept.

1. Equation: $C = 25d + 50$ is in $y=mx+b$ form.
2. Intercept ($b$): 50. This is the value when $d=0$.
3. Context: The starting cost or base fee before any days are added.

💡 Strategic Tip: The constant term is the "start". The coefficient is the "rate".

Choice B is incorrect because 25 is the rate. Choice C is incorrect because cost for 1 day is $25(1)+50=75$. Choice D is incorrect because$d$ is the variable.