Instructions: In this task, you're given passages that contain mentions of names of people, places, or things. Some of these mentions refer to the same person, place, or thing. Your job is to write questions that evaluate one's understanding of such references. Good questions are expected to link pronouns (she, her, him, his, their, etc.) or other mentions to people, places, or things to which they may refer. Do not ask questions that can be answered correctly without understanding the paragraph or having multiple answers. Avoid questions that do not link phrases referring to the same entity. For each of your questions, the answer should be one or more phrases in the paragraph, and it should be unambiguous.
Input: Passage: Jackson explored genres including pop, soul, rhythm and blues, funk, rock, disco, post-disco, dance-pop and new jack swing. Steve Huey of AllMusic wrote that Thriller refined the strengths of Off the Wall; the dance and rock tracks were more aggressive, while the pop tunes and ballads were softer and more soulful. Its tracks included the ballads "The Lady in My Life", "Human Nature", and "The Girl Is Mine", the funk pieces "Billie Jean" and "Wanna Be Startin' Somethin'", and the disco set "Baby Be Mine" and "P.Y.T. (Pretty Young Thing)".With Off the Wall, Jackson's "vocabulary of grunts, squeals, hiccups, moans, and asides" vividly showed the singer's maturation into an adult, Robert Christgau wrote in Christgau's Record Guide: Rock Albums of the Seventies (1981). The album's title track suggested to the critic a parallel between Jackson and Stevie Wonder's "oddball" music personas: "Since childhood his main contact with the real world has been on stage and in bed." With Thriller, Christopher Connelly of Rolling Stone commented that Jackson developed his long association with the subliminal theme of paranoia and darker imagery. AllMusic's Stephen Thomas Erlewine noted this on the songs "Billie Jean" and "Wanna Be Startin' Somethin'". In "Billie Jean", Jackson depicts an obsessive fan who alleges he has fathered her child, and in "Wanna Be Startin' Somethin'" he argues against gossip and the media. "Beat It" decried gang violence in a homage to West Side Story, and was Jackson's first successful rock cross-over piece, according to Huey. He also observed that the title track "Thriller" began Jackson's interest with the theme of the supernatural, a topic he revisited in subsequent years. In 1985, Jackson co-wrote the charity anthem "We Are the World"; humanitarian themes later became a recurring theme in his lyrics and public persona.
Output:
What is the last name of the person whose humanitarian themes later became a recurring theme in his lyrics and public persona?