This is a Weaken question. It asks for some new piece of evidence that, if true, would make the plan in the stimulus seem like a bad idea.
The plan is to build nursing homes to house the elderly in upcoming years (not the elderly of today). The impetus for this plan is the projected increase of 30% in the country's senior population.
The planners are assuming that the seniors in the future will actually need to live in nursing homes. The correct choice will attack the planners' assumption. It will suggest some reason why the seniors in the future will not need more nursing homes.
(B) matches the prediction and is correct. If the elderly of the future will be healthier and more fit than imagined by the planners, and will be able to live independently or with family, then the nursing homes won't be needed, and the plan is flawed.
(A) is irrelevant. Even if Country Y is not building more colleges, that doesn't mean building more nursing homes is a bad idea. It just might mean the country is passing on another potentially good idea.
(C) is irrelevant. One might think this suggests that Country Y will have trouble staffing the new nursing homes. However, this only suggests that there won't be more locally educated candidates. There may still be plenty of students to staff the new homes, or Country Y could just hire nurses and doctors from other countries.
(D) relates to how the elderly may pay for their medical needs, but has nothing to do with the plan to build more nursing homes.
(E) presents an irrelevant comparison. The plan is only about Country Y, and the costs of medication don't even relate to building nursing homes.