hook n.
1a) a curved or bent device for catching, holding, or pulling b) something intended to trap and ensnare
2) something curved or bent like a hook; esp. pl : FINGERS
3) a flight or course of a ball that deviates from a straight direction opposite to the hand of the player propelling it; also : a ball following such a course—compare slice
4) a short blow delivered with a circular motion by a boxer while the elbow remains bent and rigid
5) HOOK SHOT
6) BUTTONHOOK
7) quick or summary removal--used with get or give
8) a device esp. in music or writing that catches the attention
9) a selling point or marketing scheme

What is the correct meaning of the word hook in the sentence below?

The hook for the song was so catchy that Marie kept singing the chorus to herself all afternoon.
A.
definition 1
B.
definition 5
C.
definition 8
D.
definition 3