Read the following conversation and answer the question.

M: Hi, Lily. Where were you at lunchtime? I was looking for you in the dining hall.

W: Oh, sorry, I missed you. My English class ran late again.

M: That's been happening quite often recently. Maybe it's because the final exams are coming up.

W: Yes. After class, there is always a group of students hanging around the professor asking questions. How about you? Are yon ready for the exams?

M: I've been studying a lot recently, but my math problems are really giving me a big headache.

W: Don't worry, Tom. There's still one month to go before the exam. You have enough time to work them out.

M: Well, I don't need to spend much time on other subjects. I can pay more attention to my weak subjects.

Question: What's Tom's weakest subject? 

- Biology.

- Math.

- English.


Math.