Which is always needed to change an object’s state of motion? A.
friction
B.
an unbalanced force
C.
a balanced force
D.
gravity

B) an unbalanced force

An example would be that you push on a ball traveling in one direction, to alter the course of the ball's direction.

If a balanced force was applied, then the ball would not change velocity. For example, say you push with 10 newtons north, but a counterbalanced force of 10 newtons was aimed south, this would mean the two forces cancel each other out so to speak.

that scientist would be robert hooke

meiosis is the correct answer