The distance versus time graph for object a and object b are shown.

a graph titles distance vs time. a straight slanting line is drawn through point 7 on the y-axis and this line is labeled object a. the graph for object b is a straight slanting line passing through the origin

what is the similarity between object a and object b?

both have the same slope.
both move with variable speed.
both move with constant speed.
both start the journey from the same point.

Both move with constant speed.

Explanation:

Constant Speed Motion

When an object moves in such a way that it travels the same distances at the same times, we can say its speed is constant. For example, if it travels x=10 m in t=2 seconds and later it travels x=20 m in t=4 seconds, its speed is constant and equal to v=5 m/s. The relation between the variables x,t, and v is

x=v.t

Note that the relation between x and t is v, a constant value, thus the graph x-t is a line.

The question describes two graphs, for Object A and Object B respectively, and both of the descriptions correspond to lines. We don't have much information about the characteristics of the lines, but we can be sure, according to the definitions stated above, that both objects are traveling at a constant speed.

Both move with constant speed.