Here's a short story:

Donald was not very good at math. He could not understand the teacher's explanations . Even when the teacher explained something a second time, Donald still could not understand it. "Never mind," Donald told himself. "I am quite good at other subjects. I will cheat in the math exam, then I won't be in trouble." "I will sit next to the boy who is best at math," he thought, "and copy down his answers." The day of the exam came, and Donald sat next to Brain Smith, who always was at the top of the class in math. Donald carefully copied Brian's answers onto his own exam paper. At the end of the exam, the teacher collected the papers and graded them. Then she said, "well, boys and girls. I have decided to give a prize to the student who got the highest grade. It's difficult for me to decide who to give the prize to, however, because two students, Donald and Brian, got the same grade." "Let them share it," one of the other students said. "I thought about that," the teacher said, "but I decided to give the prize to Brian." Donald was angry when he heard this. He stood up and said. "That's not fair. I got the same grade as Brian." 'That's true." The teacher said." However, Brian's answer to Question 18 was "I don't know," yours was "Neither do I". (End of story)

Provide your best guess for the following question. Give ONLY the guess, no other words or explanation.

For example:

Guess: <most likely guess, as short as possible; not a complete sentence, just the guess!>

Here are a few examples of questions and answers:

Question: Did the two students get the same grade
Guess: yes

Question: Was one of them not good at math
Guess: yes

Question: Which one
Guess: Donald

Question: Was there one who was good at math
Guess: yes

Question: Which one
Guess: Brian Smith

Question: Did Donald cheat
Guess: yes

Question: Did the boys get the highest grade
Guess: yes

Question: Who got the prize?
Guess: Brian

Question: Who was angry
Guess: Donald

Now answer the following question in the same format.

Question: What was Brian's answer to question 18

"I don't know"