By 1980 most industrialized countries reached a fairly stable population level, but population growth in nonindustrialized countries continued at a very high rate. The most likely explanation for this difference is that
(A)Climatic shifts resulting from global warming have caused population decline in the industrialized countries
(A)The “green revolution” was rejected by industrialized countries but embraced by nonindustrial countries
(A)Farmers in industrialized countries concentrated on growing cash crops for export rather than food crops for domestic consumption
(A)Children are a more important source of labor in agricultural than in industrial societies