"Is the Grail A) a Cup, B) a Plate, or C) a Stone?" Dr Higgins asked in her Grail quiz to start off her lecture. I knew it was a cup and a plate, but the stone part didn't pop into my thinking. But I confidently concluded that the answer would be "all three," based on the cultural conventions of multiple-choice questions. I don't think anyone writes these down, yet we just absorb them. Someone from another culture, or someone who does not pick up cues because of OCD or spectrum wiring might not have absorbed them.
It was an informal asking, not a formal test. It was a game with prizes, but nothing of importance was at stake. There were three choices, not four or five, and this matters. There was no hint of an added direction of "check all that apply," which also matters. Neither was it expressly denied. If it had been five choices, with one oddly possible, like "a punk-rock medieval band," or "an invented somber color" and another rather obviously humorously wrong like "a game bird" then the convention would be different. The audience would know to pick any number of answers on their best guess, whether that was expressly stated or not.
If it were a formal test like the SAT's convention would not be enough direction. The rules would have to be spelled out. E) All of the above, and the like. Yet even in those tests there are conventions about what constitutes a fair question, and this can help you answer. They can't ask "What is the second-largest city in Vermont?" or "Are compound bows allowed in Olympic competition?" because these are niche information, not general knowledge. I was surprised that the answer to the first is South Burlington rather than Rutland, but knew that the latter is "no," which is something I happened upon years ago.
Learning these rules, formal and informal, is also a measure of intelligence. I believe SAT prep courses give you some instruction in this, and taking this type of test a few times before might be helpful. But mostly you are supposed to learn this from your other school tests (even in homeschool curricula) or entertaining magazine quizzes or study guides or Spark Notes. You develop a feel for what will be a fair question. There are people who enjoy being difficult and smarter than everyone else who think they can defend "Well actually, France isn't really a country..." or other nonsense, and they don't do well on the tests. They don't deserve to, even if they can hold forth on the subject. The testmakers also anticipate the OCD and spectrum people and their objections and have trimmed their questions accordingly, so that excuse doesn't hold.
This is part of what people mean when they say "all they measure is how well you take tests" but these are common-sense understandings of the world around you, not arcane knowledge known only to the few who go to prep schools where they teach you the secret codes. If you can't figure out that they can't and won't ask you about bass players for 90s grunge bands that's on you. You have to figure out what would be general knowledge that is fair game to be asked.