Which is an example of projectile motion?

a person throwing a rock
a child swinging on a swing set
an athlete running on a track
a teacher picking up a pencil

I believe your best answer would be Option A: A person throwing a rock.

"Projectile" is the action of something flying at a high speed, and as the child isn't flying off the swing, and the athlete isn't running so fast they are flying off the track, and lastly the teacher is only picking up the pencil; not throwing it.

Hope this helps! :)