To interpret the slope of the graph, we need to understand how it relates to the change in height of the hot air balloon over time. The slope represents the rate of ascent of the balloon.
Assuming the slope is given as a fraction of the height (in feet per 100 feet) over time (in minutes), if a line is rising steadily, it typically means that for a specific interval of time (e.g., every 2 minutes or every 4 minutes), the height increases by a certain amount.
From your options, the most plausible one seems to be:
For every four minutes that pass, the balloon rises 400 feet.
This reflects a steady ascent over time. However, if there are specific numerical values associated in the graph (which I can't see), the exact wording might vary slightly.