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).
on the matrix gives![\left[\begin{array}{cc|c}5&5&5\\1&-\dfrac23&5\end{array}\right]\to\left[\begin{array}{cc|c}1&-\dfrac23&5\\5&5&5\end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bcc%7Cc%7D5%265%265%5C%5C1%26-%5Cdfrac23%265%5Cend%7Barray%7D%5Cright%5D%5Cto%5Cleft%5B%5Cbegin%7Barray%7D%7Bcc%7Cc%7D1%26-%5Cdfrac23%265%5C%5C5%265%265%5Cend%7Barray%7D%5Cright%5D)
