An object is seen to either speed up, slow down, or change direction. these behaviors are caused
a. a balanced set of forces
b. stable factors
c. unbalanced forces
d. frictional force

C. unbalanced forces

Explanation:

That is what unbalanced forces do

< > according to newton's third law of motion, forces always act in equal but opposite pairs. another way of saying this is for every action, there is an equal but opposite reaction.< >