Angelo walks slowly to school, stays at school for the entire school day, and then walks at a faster rate all the way home without stopping along the way.
This means that it would take him more time while going to school since he walked slowly and it would take less time while going home since he walked faster.
Expect a less steep slope while going to school and expect a steeper slope while going home.
The first graph depicts such a scenario.
Notice that the distance in both cases (going to school and coming back from school) remains the same.
Therefore, the first graph is the correct graph.