Question 2
On a velocity–time graph, what does the area of the region under the line represent?
The right answer is the one marked above.
The displacement. On a velocity–time graph the x axis carries time and the y axis carries velocity. An area is those two multiplied together:
velocity × time = displacement
So the numerical value of the area covered by the graph equals the displacement. This holds just as well for a uniform velocity (a rectangle) as for a uniform acceleration (a triangle or a trapezium).
Acceleration comes from the gradient, not from the area.