A. This is not the best answer. Accidents in young adulthood might be explained as an influence of the microsystem (e.g., workplace, neighborhood) or exosystem (e.g., availability of mass transportation, poor regulation of industry).
B. This is not the best answer. Poverty might be explained by microsystem (e.g., neighborhood, education) or exosystem (e.g., educational system, social policy) or macrosystem.
C. This is not the best answer. Lifestyle might be explained by the microsystem (e.g., family patterns), by mesosystem, or by the chronosystem (e.g., the influence of fast food, acceptance of drinking and smoking).
D. This is the best answer. Health habits are certainly influenced by all of the other systems, but it is the factor over which we have the greatest amount of personal control.
E. This is not the best answer. Education is influenced by each of the other systems in some respect; the microsystem (e.g., school, home, peer group), exosystem (e.g., educational system, government policy), and macrosystem (e.g., beliefs about the value of education, economic capacity to support public education)