Which of the following reproduce by spawning?

The process of spawning is a method of reproduction primarily observed in aquatic animals, particularly among various species of fish. During spawning, female fish release eggs into the water, which are then fertilized by male fish. This method allows for the dispersal of eggs over a wide area, increasing the chances of survival for some of the offspring in a larger aquatic environment where they may find shelter and food.

In contrast, the other groups mentioned have different reproductive methods. Birds typically lay eggs in nests, where they incubate and care for them until they hatch. Mammals give birth to live young, with most providing parental care after birth. Reptiles also lay eggs but do not typically engage in the external fertilization process characteristic of spawning. Thus, the unique reproductive process of fish involving external fertilization through spawning is what sets it apart from the other options in this question.