Retrogressive metamorphosis is found in
A. Hemichordates
B. Urochordata
C. Cephalochordata
D. Cyclostomate

Hint: Metamorphosis is the phenomena in which there are converts which transform the organism from its juvenile stage (initial stage) to adult stage (end stage. In the situation of retrogressive metamorphosis, the larva possesses the advanced features that get lost during the development stage. The adult is sedentary or degenerated with the key characters. Retrogressive metamorphosis is a characteristic of ascidians. They belong to the group of Urochordates also known as Tunicates.

Complete answer:
Option – A – Hemichordates-
Hemichordates are a deuterostome phylum, the sister group to echinoderms, as well as the close relation to chordates. They have been used to gain insights into the formation of deuterostomes along with chordate body plans. Developmental studies of this group have a long as well as their distinguished history.
Option – B – Urochordata
A tunicate is a marine invertebrate animal, a member of the subphylum Tunicata. It is part of the Chordata that is a phylum which consists of all animals with dorsal nerve cords as well as notochords. The subphylum was at one time known as Urochordata, and the term urochordates is still sometimes used for these animals.
Option – C - Cephalochordate
A cephalochordate is an animal that belongs to chordate subphylum, Cephalochordata. They are chordates with all 5 types of synapomorphies, the key characteristics of all chordates during the larval or adulthood stages. These synapomorphies consists: notochord, dorsal hollow nerve cord, endostyle, pharynx as well as post-anal tail.
Option – D – Cyclostomate
Cyclostomata is a group of agnathans that can be the living jawless fishes such as the lampreys as well as hagfishes. Both groups have jawless mouths with horny epidermal structures which function as teeth, along with branchial arches that are internally positioned instead of external as in jawed fishes.

Thus, the correct answer to the question is option B “Urochordata”.

Note: The active as well as alert larva metamorphoses into a retrograde along with a sedentary bag-like creature. The adult remains closely attached to a rocky substratum.