Respuesta :
Frank is the answer because pronouns and nouns have a singular subject so it'll be a person and a person is Frank
Let's see... This is third person, right? So that eliminates I. This relates to only one person, leaving Frank as the answer because Frank is a singular third-person pronoun.
"When Frank leaves for work in the morning, he makes sure to pack his thermos."
"When Frank leaves for work in the morning, he makes sure to pack his thermos."