The answer to this question would be Store A. This question is basically asking you to find the slope that is the least, which you can find by either using the slope formula or by looking at the graph. Just take a value for example. Ill take 6 pounds of apples as an example. We can see that Store A charges somewhere between $4 and $5 for 6 pounds of apples. Store B charges $6 for 6 pounds of apples. Store C charges somewhere between $7 and $8 for 6 pounds of apples, and Store D charges over $10 for 6 pounds of apples. If you look at the graph, you can see that Store A's prices has the smallest slope, meaning that you will get more pounds of apples for less price.
Hope this helps! :D Feel free to ask me questions about my explanation, or ask any more questions that you have!