If you guessed on 10 questions completely randomly, you can figure out your probabilities of different scores with a binomial distribution.

https://www.desmos.com/calculator/uvbktuq2ci

The orange curve h(x) shows cumulative probability, so you can use it to figure out the probability of your score being between x1 and x2 by subtracting h(x1) from h(x2). For instance, there's an 80% chance that you'll get more than 1.381 of the 10 questions right.

Not surprisingly, the median and mean are around 2.5. You'll most likely get 2 or 3 of the questions right. The good news is that your distribution is skewed right, with a median greater than mean and a long upper tail. So you still have a decent chance of doing better.

Plus, there's always the chance that the college board will throw out any particularly weird questions.