The standardized test organizations give briefings to teachers on the most common Hans cues for students. In order, they are differing answer length, answers that mirror the question's grammar, and the infamous letter C.
I had to Google for the 'infamous letter C'. In case others were wondering, it seems to stem from folk wisdom still perpetuated that for a blind guess the third answer when given 4 or more options in a multiple choice test is more likely to be correct than the others.
The linked article suggests this does not hold (for the ACT), but doe suggest picking a single letter and sticking with it for all blind guesses would outperform a purely random guessing strategy.
