I think the correct answer is D. to compare the present with the earlier, non-mechanical times.
Letter A. is incorrect because the text brings us to the conclusion that Earth is not suitable for biological life anymore. There has been a nuclear war or something like that and the only things that "survived" are the mechanical ones like the haouse or the mice. Some animals are still alive but have miserable lives.
Letter B. is also incorrect because since the beggining we can observe that no humans live there anymore. The chores the mechanical house keeps doing make clear they are gone.
Letter C. states that scientific advances create the perfect society but despite these advances humans ruined an entire planet leaving no room for a society itself.
Letter D. is the correct answer because as the mechanical house keeps doing its chores, it shows us how people lived in the past. The kids played, the family had breakfast, the man mowed the lawn, etc. Now the times changed and nothing of that exists anymore.