If one smokes cigarettes, you run the risk of getting lung cancer.

number
mood
tense
person

my Answer D the key word is you and you is a person and is the subject of the sentence

Right.

Your analysis is correct. In the given sentence, the number is singular because it refers to one person. The mood is indicative as it presents a fact or statement. The tense is present simple, indicating something that is true in general. The person is second person, as indicated by the pronoun "you" which is addressing the person directly.