If the pain in your knee continues, l advise... a doctor. a. you see b. to see c. you to see

The correct answer is b. to see.

The complete sentence would be: "If the pain in your knee continues, I advise to see a doctor."

However, the more common and grammatically correct phrasing would be: "If the pain in your knee continues, I advise you to see a doctor." But from the given options, "to see" is the best choice.