The plural subject pronoun you would use to talk about Felipe and Arianna (they) is "ellos".
The correct answer is "ellos." To arrive at this answer, you need to consider the gender of the people being referred to. Felipe is a male name, so he is referred to as "él" (he). Arianna is a female name, so she is referred to as "ella" (she). When referring to both Felipe and Arianna together, you would use the plural subject pronoun "ellos" because it includes both male and female individuals. So, the correct plural subject pronoun in this case is "ellos."
