If the child share is declining while the working-age group is still very large, what demographic phase may this indicate?

Correct answer: Phase of demographic opportunity

A declining share of children usually suggests that fertility has fallen, so fewer new children are being added relative to the total population. If the working-age group is still very large, the country may be receiving the benefit of a large generation born earlier, now entering or occupying productive ages. When the working-age share is high and the dependent child share is falling, the dependency burden can temporarily decrease.

This situation is called a demographic opportunity or demographic dividend window. It can support faster economic growth if people receive education, skills, health care, and sufficient employment. The opportunity is not automatic; good policies and jobs are needed to convert the age structure into gains. Thus option A is correct. The other choices either describe an unrelated extreme or incorrectly assume that high elderly dependency or very high fertility must be present.