Answer:
the second answer from the top
Explanation:
the graph has to go through the point (3, 15), which stands for 15 miles in 3 hours. and therefore also through (6, 30), (9, 45), (12, 60), ...
in other words, with every 3 additional hours we get 15 additional miles. or simplified, with every additional hour we get 5 additional miles.
3/15 = 1/5 = 6/30 = 12/60, ...
and only the second graph shows this.
the slope is officially defined as (y change / x change).
therefore, in our case
15/3 = 5/1.