The timing of puberty has changed over the past few generations.What does this trend likely reflect

A)  an increase in pollution 
B)  improvements in nutrition and medical care 
C)  increases in sexual activity at an earlier age, triggering earlier pubescence 
D)  changes in genetically predisposed timing of puberty

Puberty

The stage of human development during which children become sexually mature and capable of reproduction, marked by physical, hormonal, and emotional changes.

Nutrition

The science that interprets the interaction of nutrients and other substances in food in relation to maintenance, growth, reproduction, health and disease of an organism.

Medical Care

The provision of services by healthcare professionals to diagnose, treat, and prevent illness, injury, and other physical and mental impairments in individuals.