Concept:Fusion of gametes from two parents defines sexual reproduction.Explanation:Gametes are specialized reproductive cells, such as sperm and egg.When a male gamete fuses with a female gamete, the process is called fertilization.This fusion produces a zygote.The zygote develops into offspring with genetic traits from both parents.Asexual reproduction, binary fission, and budding do not involve fusion of gametes from two parents.Answer:A. Sexual reproduction