Acontact force is a force which

a. can occur over long distance.

b. occurs when two objects are near enough to influence each other.

c. occurs when two objects are touching each other.

d. can occur over short distances.

A contact force is a force which  occurs when two objects are touching each other. (C)

A contact force is a force that occurs when two objects are touching each other.

C.occurs when two objects are touching each other.

Explanation:

In contact force, two objects need to touch each other for the force to happen. This force is ubiquitous and requires contact for the force to occur. It is responsible for most visible interactions to occur.  

Examples of contact forces include moving a couch, pushing a desk, kicking a ball, or pushing a car up a hill. In kicking a ball, the contact force happens with a short impulse, whereas while moving a vehicle, a person continuously applies the contact force.

c) up

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