The correct option is B Caenorhabditis elegans
Developmental biology is the study of the process by which animals and plants grow and develop, and is synonymous with ontogeny. However, for research in developmental biology in recent years, scientist have focused on the use of model organisms. The roundworm Caenorhabditis elegans is used exclusively in research for elucidating biological processes as it has very defined development patterns involving fixed numbers of cells, and it can be rapidly assayed for abnormalities.