Which of the following is an example of a contact force?

Responses

a skydiver in freefall
a skydiver in freefall - no response given

a magnet pulling a screw toward it
a magnet pulling a screw toward it - no response given

a person standing perfectly still on the ground
a person standing perfectly still on the ground - no response given

rain falling from the sky

rain falling from the sky - no response given