The correct option is B he
A relative pronoun functions as a pronoun as well as a conjunction, as a pronoun it refers or relates to the noun that is common in both sentences, and as a conjunction it combines those sentences. The antecedent is the noun that the relative pronoun refers to, and the latter usually follows immediately after the former. For example in, 'The lady whom i met yesterday...', here 'whom' is a relative pronoun that relates to the antecedent, 'lady'. In some cases, the antecedent is usually implied in the sentence when it's a general statement, and hence it can be omitted. Like, in the given sentence, "Who" is a relative pronoun, and it is not preceded by the antecedent. From the given options, 'He' is a pronoun that is implied, as it refers to a person in general terms, hence option B is correct. 'Who' is a relative pronoun that relates to the antecedent, and not an antecedent itself. Hence, option A is incorrect. 'Does' is a verb that performs the action 'to do', it's not the antecedent here, hence option C is incorrect. 'Will' is a modal auxiliary, auxiliary verbs determine the mood or tense of a sentence, 'will' refers to the future tense. As it is a verb, option D is incorrect.