A child's development is affected by

Child development is not the product of a single cause; it is a continuous process shaped by the interaction between heredity — the genetic potential inherited from parents, such as the range for intelligence, physical build, and temperament — and environment — the external physical, social, cultural, and educational conditions a child grows up in. This interactionist view is the standard position in developmental psychology and pedagogy: heredity sets the range of possibilities, and environment determines how much of that potential is actually realised.

Applying this to the item: heredity alone cannot explain why children with similar genetic backgrounds show different developmental outcomes when raised in different settings (nutrition, family, schooling), and environment alone cannot explain inherited differences in temperament, physical growth rate, and cognitive potential seen among children raised in very similar settings. Because both factors continuously interact — nature supplying the raw potential, nurture shaping its expression — the accurate description of what affects a child's development is heredity AND environment together, not either one exclusively.

This also rules out the narrower options: heredity alone (the nativist position) and environment alone (the strict behaviourist position) each capture only half of the picture, while culture is only one strand of the broader environment (alongside family, nutrition, and schooling) and does not by itself account for the hereditary contribution. The interactionist model — development as the joint product of heredity and environment — is the position accepted across mainstream developmental-psychology and pedagogy curricula, including the REET syllabus this item is drawn from.