Retrogressive evolution is shown by
a) Man
b) Birds
c) Tunicates
d) Fish

Hint: Retrogressive evolution is the opposite: when the organism reduces its complexity or begins to forsake more advanced characteristics in favor of more primitive ones. It's called devolution.

Complete answer:
Retrogressive evolution is a process in which complex forms of the organism develop into a simpler form. For example, monocot plants belong to a more advanced group of herbaceous and simple-structured plants.
Metamorphosis is a change from the juvenile stage to the adult stage in which the larval stage is quite different from the adult stage. Retroactive metamorphosis is a type of metamorphosis seen in Herdmania (and other urochordates). It involves the transformation of an active, free swimming larva with advanced characters into a sedentary, simple adult. As a result, retrogressive metamorphosis, retrogression or degeneration shows that larva forms an adult.
In retrogressive metamorphosis, the larva has advanced characters that are lost during development, and the adult is either sedentary or degenerate with primitive characters. Urochordata adults, sedentary show degenerative characters, while free swimming Tadpole larva shows advanced chordate characters that are lost during metamorphosis. In tunicates and amphibians, tadpole larvae are formed, which undergo retrogressive changes to become adults.

Thus, the answer is option C: Tunicates

Note:
Some tunicates live as solitary individuals, while others reproduce by budding and become colonies, each unit being known as a zooid. They are marine filter feeders with a water-filled, sac-like body structure and two tubular openings, known as siphons, through which they draw and expel water.