Well, this wasn’t something I remembered reading about in the driver’s handbook, but common sense told me that (b) was correct. After all, leaving your car for help in the middle of a snowstorm will most likely put you into more danger, while running your car to prevent carbon monoxide poisoning is just ridiculous. And if (a) and (c) are incorrect, then (d) must be, too.
What?! How does that even make sense?
Lesson learnt today: Do not trust whatever unofficial practice quizzes say, EVER. Use their services with caution, and make sure you study directly from the official material first (and right before your test too, to prevent wrong information from clouding your memory).