Select all correct answers which three classes of animals practice internal fertilization

mammals, birds, & reptiles. :)
explanation: The mammals, birds and reptiles are the three classes in the animal kingdom that practice the internal fertilization. These three classes, that is the birds, mammals, and the amphibians, always use fertilizes the egg internally. The amphibians on the other hand fertilizes externally. The arthropods, on the other hand, reproduce both by external fertilization and internal fertilization.

3. is true i think i should be right