The correct answer is: D. Muscular force.
Contact force is a force that is exerted between two objects that are in contact with each other. Muscular force is a type of contact force that is exerted by muscles. Friction, magnetic force, and electrostatic force are not contact forces.
Friction is a force that opposes the relative motion of two objects that are in contact with each other. Magnetic force is a force that is exerted between two objects that have a magnetic field. Electrostatic force is a force that is exerted between two objects that have an electric charge.
Muscular force is a type of contact force that is exerted by muscles. Muscles are attached to bones by tendons. When a muscle contracts, it pulls on the tendon, which causes the bone to move. Muscular force is used to move the body, to lift objects, and to perform other tasks.
Here are some examples of muscular force:
- When you walk, your muscles contract to move your legs.
- When you lift a weight, your muscles contract to move the weight.
- When you write, your muscles contract to move your hand.
- When you speak, your muscles contract to move your mouth.
Muscular force is a very important force that allows us to move and perform many tasks.