Which of the following is not a non-contact force?

• A magnet can exert a force on another magnet or magnetic material even when they are not in contact.  
• The electrostatic force is the force exerted by a charged body on another charged body. These charged bodies need not be in contact.
• The gravitational force is exerted between objects having some mass and these bodies need not be in contact. For example, the force exerted by the earth on the moon. 
• Frictional force is exerted when the surfaces of two bodies come in contact with each other. 

Therefore, frictional force is not a non-contact force.