Answer:
Ordinarily a graph like this will have arrowheads on the ends of the curve, indicating the curve continues on in the same direction. Here, we have to assume the existence of such arrowheads in order to choose a sensible answer.
As x goes to -∞, the curve continues to increase toward +∞. This is not an answer choice.
As x goes to +∞, the curve continues to decrease toward -∞. This matches the third answer choice.