Answer:
Section A: Sally drives from her house to her friend's house.
Section B: Sally stops to visit her friend.
Section C: Sally drives from her friend's house to the post office to drop off a card.
Section D: Sally drives back to her house.
Explanation:
As you can see in the graph, the point (0,0) is the location of Sally's house. In that point the distance is 0 and the time is 0.
In Section A she drives 3 miles in 6 minutes from her house to her friend's house.
In Section B, the distance does not change, this means that Sally stopped at her friend's house for 4 minutes.
In Section C she drives (for 4 minutes) 1 mile from her friend's house to some place (In this case the post office).
In Section D she comes back to 0 distance, then, she drives back to home.