Answer:
D. turned out to be pretty enjoyable once I started doing experiments myself.
Explanation:
An intensive pronoun is the use of reflexive pronouns to add emphasis on the noun or pronoun in the sentence. Examples of such intensive pronouns are "myself, himself, herself, itself" etc.
Among the given examples in the question, the intensive pronoun is used in the fourth sentence. The intensive pronoun used is "myself" which emphasized the speaker. Therefore, the sentence is
My science class turned out to be pretty enjoyable once I started doing experiments myself.
Thus, the correct answer is option D.
