Answer:
It is given that a car traveling at 23 mi/h accelerates to 46 mi/h in 5 seconds.
This means that in 5 seconds it's speed continuously increases to reach 46 mi/h from 23 mi/h.
It maintains that speed for 5 seconds and then slows to a stop in 5 seconds.
This means that the speed of the car is constant i.e. 46 mi/h i.e. the graph is a straight horizontal line parallel to the time axis.
And then it decreases to reach 0 mi/h.