Final answer:
The correct answer is d. external fertilization, which is suitable for animals with limited mobility as it allows the water to carry sperm to eggs.
Step-by-step explanation:
The form of reproduction that is useful to an animal with little mobility that reproduces sexually is d. external fertilization. During external fertilization, the male and female gametes are released into the environment, where fertilization occurs. This method is commonly found in aquatic species, where mobility may be limited, but the water can carry sperm to eggs, thus facilitating the process of reproduction. Unlike fission, budding, and parthenogenesis, which are forms of asexual reproduction, external fertilization involves the combination of genetic material from two different individuals, thereby producing genetically diverse offspring.
An animal with little mobility that reproduces sexually would likely benefit from external fertilization.This form of reproduction involves the release of eggs and sperm into the environment, where fertilization takes place outside of the body. It allows for the mixing of genetic material from different individuals and can result in diverse offspring.In contrast, fission, parthenogenesis, and budding are all forms of asexual reproduction, which would not be as useful for an animal with limited mobility looking to produce genetically diverse offspring.