ANSWER
The second graph correctly models their elevation over time
Step-by-step explanation
We have to find the height difference between each point:
Each square in the graph represents 15 minutes of time.
Between A and B there are 30 minutes and 800 feet of height difference → They begin running uphill 800 feet for 30 minutes.
Between B and C there are 15 minutes and -400 feet of height difference → then run downhill 400 feet for