Final answer:
A straight line on a distance/time graph indicates the object has a constant velocity. This constant slope shows that there is no change in speed or direction, representing uniform motion.
Step-by-step explanation:
In a distance/time graph, if there is a straight line, we know the velocity isn't changing. This is because a straight line on a distance/time graph indicates that the object is moving at a constant speed in a specific direction, hence a constant velocity. The slope of the line represents the velocity, which in the case of a straight line is uniform. This type of motion is known as uniform motion.