Which sector would experience a rise in population in a country undergoing a rapid population decline? 

A)  the portion of the overall population comprised of younger people 
B)  the portion of the overall population that are not threatened with labour shortages 
C)  the portion of the overall population that is consuming a large fraction of medical services 
D)  the portion of the overall population that is not on social security

Population Decline

A decrease in the number of individuals in a species or population, often due to environmental pressures, loss of habitat, or human activities.

Medical Services

Professional services provided by individuals in the healthcare industry to treat and maintain patients' physical and mental health.

Labour Shortages

A situation in which there are insufficient workers available to fill the existing job vacancies in certain industries or regions.