In which condition will the effect of health services on population change be most visible?

Correct answer: The death rate falls after health improvement

Direct answer: A, when the death rate falls after health improvement. Health services affect population change most directly through mortality. Better hospitals, medicines, vaccination, sanitation, maternal care, and treatment can prevent or manage disease and reduce avoidable deaths. Step by step: health facilities and preventive measures improve; illness is treated or prevented more effectively; fewer people die from preventable or treatable causes; the death rate falls. If births remain greater than deaths, natural increase may also become larger, but the immediate measurable link in this question is the fall in death rate. B describes a physical change in drainage, not the demographic effect of health care. C concerns soil and has no direct connection with mortality. D concerns the size of a territory, not the health of its population. Memory cue: health services influence population mainly through survival and mortality; do not confuse a geographical change with a demographic one.