The verb, ser, is in the singular el/ella/usted tense, meaning that the subject is only one person or thing. This eliminates the two middle choices, as they are multiple people.
Next, the adjective. Alto is in the masculine form, so Maria, as it is a girl name, is also able to be eliminated.
J.F Kennedy era un líder muy famoso. Tiene pelo rubio y una esposa muy guapa. El era muy dedicado y valiente. Yo pienso que el era un líder por que no era malvado y cobarde.
