Answer:
The correct option is B. Jim promised himself a reward for working so hard.
Step-by-step explanation:
Intensive pronouns, also known as emphatic pronouns, are pronouns used to refers back to another noun or pronoun previously said in the sentence in order to emphasize it. Such intensive pronouns are myself, yourself, herself, himself, itself, ourselves, yourselves, and themselves.
Bearing the above in mind, it could be said that from the options provided the sentence contains the intensive pronoun is Jim promised himself a reward for working so hard.