At the time I took my test, my state listed 13 different references they pulled questions from for the unlimited licence. I opted to get and study six of them by making the assumption there would only be one or two questions from each of the rest and I only needed a 70% to pass. I remember seeing three questions total on things I didn't study including one on the gases used to make neon type signs.
Was the answer Neon?
Without knowing the question, I would guess would be the noble gases. Neon, Xenon, Argon, etc.
In my humble opinion, the best way to take any test is to answer all questions you know or think you know immediately then move on to the next question. If you do not know the immediate answer that question, move on to the next one, and the next one. You might run into a string of five questions that you are unsure of the answer, do not let these five questions burn an hour of your time, move on. Chances are the next 20 questions will be a piece of cake, or much easier then the ones you did not know. This has nothing to do with a specific test, rather test-taking in general.
Here, in Virginia, you need an 80% + score to pass a driver's test...DMV. usually it's 25 questions, as soon as you get 20 right, the test ends, it doesn't matter if you haven't even looked at the last page questions yet. Conversely, as soon as you get six wrong answers, the test is over, you failed. Go to what you know then come back and play multiple guess or research later when you have time, don't burn up all your time early on questions that may not matter for a passing grade.