Ok so I have a calc exam tmrw and I am having a hard time with slope fields. My professor told us that on the exam he is going to give us the slope field (graph) and we are going to have to pick one differential equation from a set as the one that matches the graph.

SO my question is: how can you tell which slope field pretains to what graph? What are the rules in figuring that out?

Please help ASAP!