A displacement–time graph is a straight line through the origin, rising evenly from 0 m at 0 s to 40 m at 10 s. The graph shows:

Correct answer: (a) An object in uniform motion

Explanation

In a displacement–time graph, the slope gives the velocity. A straight line has a constant slope, so the velocity is constant:

• here the slope is 40 m ÷ 10 s = 4 m/s throughout;
• equal displacements are covered in equal intervals of time.

So the graph shows uniform motion. A stationary object would give a horizontal line, and constant acceleration would give a curve (a parabola) whose slope keeps increasing.