The author of passage 1 would probably respond to the reference in passage 2 to the “social isolation inherent in living alone”by

Answer:
The author of passage 1 would probably respond to the reference in passage 2 to the “social isolation inherent in living alone” by referring to the results of the study mentioned in passage 1.
Explanation:
In the given two passages, the authors talk about the pros and cons of living alone. While passage 1 directs the arguments to the advantages and positive nature of why people live alone, passage 2 contradicts that argument.
Passage 2's argument that "social isolation [is] inherent in living alone" can be best responded to by the author of passage 1 by referring to the study results in passage 1. This is because passage 2 states that living alone makes a person more isolated which is contrasting to the claim made in passage 1. The author of passage 1 instead states that living alone "is the best of both worlds: community when you want it but guaranteed peace and quiet whenever you need."
Thus, the correct answer is the first option.