A raised island splits the road ahead of you and a black-and-white KEEP RIGHT sign stands at the near end of it. What is that sign settling for you?

Correct answer: A. You must pass the obstruction on the right — where either side is allowed, a double arrow sign is used instead

Which side of the obstruction you are allowed to use. Book 5 says the purpose of the KEEP RIGHT and KEEP LEFT signs "is to indicate to drivers that they must keep their vehicles to the right or left, respectively, of obstructions or roadway features" — raised or depressed median strips, loading islands, refuge islands, traffic islands and central piers — and that the sign "must appear at the approach end (upstream end) of the obstruction." The detail worth carrying is what its presence rules out: "If vehicles can pass on both sides of an obstruction, a KEEP RIGHT or KEEP LEFT sign is not used", and a DOUBLE ARROW sign is used instead. So a KEEP RIGHT sign is not advice about the tidier side — it means one side only, and it is the right.

Source: MTO Driver's Handbook: Ontario Traffic Manual, Book 5 — Regulatory Signs (December 2021), Section 10 — KEEP RIGHT Sign (Rb-25R) and KEEP LEFT Sign (Rb-25L)