OE: (D) The author is arguing that placing homeless animals with senior citizens would help reduce the number of pets and bolster the health of their owners. The support for this solution is twofold; that seniors who live with others have fewer health problems, and that animals are frequently happier with older owners. The author makes the assumption that the connection between living with others and health problems is a causal one, and that it is the companionship of living with others, specifically, that provides the health benefits. If, instead, the benefit comes from those family members providing nursing care, then it is less likely that living with a pet would provide the same health benefits as living with another person. Knowing the reason for the health benefits is important to evaluating whether the proposed solution would actually benefit humans.
Choice (A) is incorrect because it addresses the feasibility of the solution and how widely it can be implemented. Whether or not most of the animals would be suitable is irrelevant, as long as those animals that are suitable are the ones that are placed with senior citizens.
Choice (B) is even further outside of the realm of the argument; the costs of the program are not at issue.
Choice (C) raises a potential concern about placing animals with seniors, but this concern is eliminated by the information that part of the solution would include providing assistance in caring for the adopted animals.
Choice (E) is incorrect because the author is not suggesting that the proposed solution is the only one, or the best one; merely that this solution would be of benefit to animals and people.