The flippers of penguins and dolphins are examples of convergent evolution. Convergent evolution occurs when different species independently evolve similar traits or structures because they adapt to similar environments or ecological niches, despite being of different lineages. This phenomenon leads to analogous structures, which perform similar functions but are not derived from a common ancestral trait.

Penguins are birds, and dolphins are mammals. Their ancestors did not possess flippers, but both these species have evolved this similar structure, which helps in swimming efficiently in aquatic environments. The development of flippers in both cases is an adaptation to enhance their abilities in similar environments (aquatic life), even though they come from different evolutionary paths.

Therefore, the correct answer is:

Option C: Convergent evolution