A NO LEFT TURN sign carries a black tab beneath it reading "EXCEPT AUTHORIZED VEHICLES". You have a good reason to make that turn. Does the tab help you?

Correct answer: D. No — it exempts police, emergency and official-business vehicles such as maintenance and utility crews, not ordinary drivers with a reason

No — "authorized" is a much narrower word than it sounds. Book 5 says the EXCEPT AUTHORIZED VEHICLES tab "may be used to supplement Turn Control signs at locations where authorized vehicles are not required to comply", and then defines the term: "Authorized vehicles are those vehicles that have special permission, such as law enforcement vehicles or emergency vehicles, or vehicles performing official business, such as maintenance, construction, or utility repairs, etc." It is about who has been given permission in advance, not about how good your reason is. Two related tabs work the same way and name their class outright: BUSES EXCEPTED and BICYCLES EXCEPTED.

Source: MTO Driver's Handbook: Ontario Traffic Manual, Book 5 — Regulatory Signs (December 2021), Section 8 — EXCEPT AUTHORIZED VEHICLES Tab Sign (Rb-16t)