Student or Learner
I think 3 is more awkward. Do they ever say that? I think 4 can work.
10-2-26. Which can't replace the underlined?
G: What's the matter, Minsu?
B: I don't feel well. I have a cold.
G: Why don't you go and see a doctor?
B: I think I will.
① What about going to see a doctor?
② Why not go and see a doctor?
③ Can you see a doctor?
④ I would see a doctor if I were you.
⑤ I think you had better see a doctor.
All are possible, depending on the wider context.