You have to consider the “ends” of the x-axis, the far right (for infinitely large values of x) and left (for infinitely small values of x) of the graph.
From the diagram above you can see that:
- When
then
(notice that as the values of x get smaller and smaller, the graph gets closer and closer to the line y=1);
- When
then
(notice that as the values of x get larger and larger, the graph gets closer and closer to the line y=1).
Answer: correct choice is D.