means that he picks any of the 5 choices at random
Step-by-step explanation:
"guesses" means that the student will pick at random any of the 5 choices that he has with the hope to select the right one. Then we are assuming that any of the 5 choices are equally likely to be the correct one , so there is no answer that is closest to be the right one ( we do not have any information that can judge whether any answer is more likely to be the right one with respect to the others).
