On a separate sheet of paper, draw a v-t graph that represents an object moving at a constant speed of 60 mph for a period of 10 hours. on this graph the line you drew to represent constant speed is. a. perfectly vertical b. perfectly horizontal c. diagonal d. curved

It will be perfectly horizontal. Since it’s a V-T graph, we will represent velocity on the y-axis (vertical axis) and time on the x-axis (horizontal axis).

Let’s think — a constant speed is one that doesn’t change.
At every point in time, the velocity will be 60, no matter what. On the other hand, time can’t be constant. Time will always be progressing, even though the velocity is the same.

This means the graph will only be moving along the time axis (the horizontal axis), showing how time has changed, but the velocity has not (the graph will always be at the point of 60mph for velocity, but won’t always have the same point for time).
If you need it, I can draw the graph as well.