The correct answer to the question is A) a push or pull.
Step-by-step explanation:
From Newton's first laws of motion we know that everybody continues to be at state of rest or of uniform motion in a straight line unless and until it is compelled by some external unbalanced force.
Hence,the force is an external agent which is responsible for creating the motion in a body.
It can be defined as a pull or push which creates or destroys the motion of a body, increases or decreases the speed of a body, or changes or tends to change the direction of motion of a body.
Hence, the correct answer to the question is that force can be expressed as a push or pull.