The Higher Fertility Rates Experienced by Low-Income Countries Are Partially

The higher fertility rates experienced by low-income countries are partially explained by the fact low-income countries

A) are more industrialized than middle-income countries,so they need more wage earners.
B) have more crowded urban centers than high-income countries.
C) are more likely to send children to school for longer periods of time.
D) have more agricultural than industrial economies,making children important sources of labor.