Wrong, it was lemon.
It would need to balance strawberry as chocolate balances vanilla, and strawberry ice cream is sweet, a little tangy and fruity.
Banana isn't tangy, but it's sweet and fruity, so it's too close. Lemon, being less sweet, more tangy, and with a citrus flavor instead of a fruit one is the best match.Caramel is a runner-up. Not tangy at all, sweet and rich flavor.