Answer:
B
Explanation:
Stopping at a stoplight means that Chris's speed would be zero on the graph. The times that his speed is zero are times t = 0, t = 2 min, t = 11 min, and t = 21 min. Because the graph shows his speed from the time he left his house (at t = 0) to the time he arrived at the theater (at t = 21 min), the most likely times he stopped at stoplights are times t = 2 min and t = 11 min.