The correct option is B I
A noun or pronoun is said to be in the subjective/nominative when it is used as the subject of the sentence. Here, the noun 'Jacob' and the pronoun is in the subjective case as it is the subject of the verb 'walked'. Hence, we need to use the pronoun 'I' instead of 'me' because 'I' is a subjective case pronoun whereas 'me' is an objective case pronoun, which has been incorrectly used.