One of the largest challenges faced by nations with aging and declining populations is providing for citizens.
a. schools and classrooms
b. food and land resources
c. retirement and healthcare
d. adequate employment opportunities

If the nation is aging, it is not like they have more children to take care of, so it is not option A. Food and land resources won't change drastically because the age of people, so we can skip B as well. There also won't be super populations so adequate employment might not be a problem. In fact, it might be the opposite, so we can ignore D.

Which leaves us to the logical conclusion.

C. retirement and healthcare

Older people spend much more money on remedies and medical care. They are also the ones who are retiring and with too many retired people and not enough to pay for the retirement in the form of taxes, the situation creates a problem for the government.

austria

hugary

yugoslavia

czechoslovakia