Oar is to rowboat as foot is to

An oar puts a rowboat into motion. A foot puts a skateboard into motion. The answer is not choice a because running is not an object that is put into motion by a foot. Sneaker (choice b) is incorrect because it is something worn on a foot. Jumping (choice d) is incorrect because although you do need feet to jump, jumping is not an object that is put into motion by means of a foot.