Select the correct definition about tissue grafts. a. allografts are between different species. b. xenografts are between individuals of the same species. c. isografts are between identical twins. d. autografts are between two genetically identical individuals.

The correct answer is c. isografts are between identical twins.
Isograft is is a graft (transplantation tissue) between two individuals who are genetically identical (monozygotic twins). This is usually very successful transplantation between such two individuals (transplant rejection never occurs). This is because genetically identical individuals have the same major histocompatibility complex, which is usually responsible for the rejection by the adaptive immune system.