The correct answer is A. Force.
A scalar quantity is a quantity that has magnitude but no direction. Force is a vector quantity, which means it has both magnitude and direction. Pressure is a scalar quantity because it only has magnitude. Velocity is a vector quantity because it has both magnitude and direction. Acceleration is a vector quantity because it has both magnitude and direction.
Force is a push or pull on an object. It is measured in Newtons (N). The force of gravity on an object is its weight. The force of friction is the force that opposes the motion of two objects that are in contact with each other. The force of air resistance is the force that opposes the motion of an object through the air.
Pressure is the force exerted per unit area. It is measured in Pascals (Pa). The pressure of air in a tire is the force of the air molecules pushing against the inside of the tire. The pressure of water in a pipe is the force of the water molecules pushing against the inside of the pipe.
Velocity is the speed and direction of an object’s motion. It is measured in meters per second (m/s). The velocity of a car is the speed and direction of the car’s motion. The velocity of a ball thrown in the air is the speed and direction of the ball’s motion.
Acceleration is the rate of change of velocity. It is measured in meters per second squared (m/s^2). The acceleration of a car is the rate at which the car’s velocity changes. The acceleration of a ball thrown in the air is the rate at which the ball’s velocity changes.