The correct answer is D. Lower birth rates
Step-by-step explanation:
The growth rate is determined by how fast the population of a country or a zone increases. This factor is higher in developing countries than in developed countries. One factor that contributes to this is the low birth rate in developed countries as people have fewer children in these countries, and therefore there are fewer births per year than in developing countries. This is influenced by the accessibility to contraceptive methods, higher education levels, and cultural values. Also, fewer births mean the population will grow slowly, and therefore the growth rate is lower.