Which of the following distance-time graphs represent one-dimension uniform motion?
A)









B)









C)










D)

Hint: If an object goes in a straight line, that object covers the distance which can be represented by the distance time graph. Uniform motion represents a constant change in displacement per second. Distance time graph for uniform motion is a straight line, that is, equal distance is covered by the equal units of time.

Complete step by step answer:
> Option A is correct. This is because it represents the graph where change in displacement per second is constant. Therefore, velocity is constant and hence it performs uniform motion.
> Option B is incorrect. This is because change in displacement per unit time is not constant.
> Option C is incorrect. This is because there is change in velocity per unit time, so motion is not uniform. It is non uniform motion.
> Option D is incorrect. This is because change in velocity is given, so there is no point to discuss uniform motion. Change in velocity means motion is non uniform.

Distance time graph for uniform motion in one dimension means equal distance is travelled by equal interval of time, that is velocity is constant and hence the acceleration becomes zero.
Therefore, Option A is the correct answer.

Note: Change in displacement per unit time should be constant for a body to undergo uniform motion. The area under the speed and time curve represents the total distance travelled.