Any force that causes an object to move in a circle is called a(n)
a. balanced force.
b. unbalanced force.
c. gravitational force.
d. centripetal force.

A). balanced force
b). unbalanced force
There's no such thing as either of these.  A group of two or more forces can be balanced or unbalanced.  A single force can't be.

c). gravitational force ... doesn't cause an object to move in a circle;
     Drop a stone from the roof of a tall building and watch it fall.
     It goes straight down, not in a circle.

d). centripetal force ... force directed toward the center of a circle,
     causes an object to move in a circle.

Answer ( slope);