Answer:
In a linear equation, like the ones in the graphs, the slope is equivalent to the rate of change. And we know that speed is defined as the rate of the position, thus the slope of these lines is exactly equal to the speed.
From this, we will see that the correct option is D.
Knowing this, two runners will have exactly the same speed if and only if both slopes (one for each runner) are exactly equal. This means that we will see two parallel lines.
This makes a lot of sense, because if they run at the same speed, then they will never meet (like two parallel lines), instead if they run at different speeds and the one that is behind runs faster, at some given point the one that goes last will reach the other, and in this point we would see that the lines intersect in the graph (like in options A, B, and C).
So from this we already can see the correct option, it is the graph with the two parallel lines, the graph D.
Explanation:
