Choice A is the correct answer.

• Quadratic ($a < 0$): Parabola opening downward (Hill shape). Goes up, peaks, goes down.
• Quadratic ($a > 0$): Parabola opening upward (Valley shape). Goes down, bottoms out, goes up.
• Linear: Always goes up or always goes down.
• Exponential: Always increases or always decreases.

Choice B is incorrect because it goes down then up. Choice C is incorrect because it only goes up. Choice D is incorrect because it only goes up.