If you can eliminate even one answer, you increase your chances of getting the question right. Statistics show that it's worth guessing in such situation. With each correct answer you gain one point; if you leave the answer blank you get no points; if your answer is wrong, you only lose 1/4 points.

The better you get at eliminating implausible choices, the more points you will pick up from educated guessing. But no matter what, if you have time to read through a question and eliminate at least one choice, it is always to your benefit to guess. As long as you are guessing better than randomly, you will do considerably better.