The distance versus time graph for object a and object b are shown. which object moves with changing speed?

Both: Object A and Object B, because different distances are traveled in the same time interval

Explanation:

Constant Speed Motion

An object is said to have constant speed it travels same distances at the same time intervals. For example, an object who travels 4 meters in 2 seconds has a constant speed if it also travels 6 meters in 3 seconds and 10 meters in 5 seconds. The constant speed is 2 m/s.

We can see in the image provided two graphs of distance vs time of two objects. If they were traveling at a constant speed, that graph should be a single line (increasing, decreasing of horizontal). None of the graphs show a line, which indicates the object some times travels more or less distance in a given time interval than in other equal time intervals. Thus, the answer is the last option:

Both: Object A and Object B, because different distances are traveled in the same time interval