The correct answer is option C) exploration of different niches, avoiding competition between life stages.
Each phase of development presents a different habitat and niche, which prevents competition between species, that is, intraspecific competition. In this way, the effectiveness of the animal within its environment is increased, as well as its adaptation to the environment.
The other alternatives highlight stages of development that exist, but are not related to the increase in the number of species or to the justification presented.