Retrogressive metamorphosis occurs in
 A. Hemichordata
 B. Cephalochordata
 C. Urochordata
 D. Vertebrata

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Hint: In retrogressive transformation, the hatchling has progressed characters that are lost during the turn of events and the grown-up is either inactive or deteriorated with crude characters. Transformation is a change from the adolescent to the grown-up stage where the larval stage is very not the same as the grown-up stage.

Complete answer:
Retrogressive transformation happens in Urochordates. In retrogressive transformation, the hatchling has progressed characters that are lost during the turn of events and the grown-up is either inactive or deteriorated with crude characters. Urochordate grown-ups, being inactive show degenerative characters while the free-swimming fledgling hatchling shows progressed chordate characters that are lost during transformation. Parasitic scavengers, as Sacculina and copepod parasites and stylopids and scale bugs (Insecta) likewise show the retrogressive transformation.

Additional Information:
The serious Chordate characters of the hatchling
There is a bar like a notochord in the tail to which are joined muscle groups for swimming. There is a dorsal empty nerve rope which is broadened to shape the mind at the foremost end. A photoreceptor ocellus and an adjusting organ, the statocyst is appended to the mind. There are just two sets of gill cuts in the pharynx however the mouth is shut by a film and the digestive tract is simple. Endostyle on the ventral side of the pharynx is very much evolved which capacities like thyroid organ and aides in transformation. The heart is on the ventral side of the gut however is non-useful. The hatchling has on the foremost end three ectodermal cement papillae which help in firm connection on the base.

So, the correct answer is ‘Urochordata’.

Note: The fledgling hatchling of Herdmania is just 1-2 mm long when it incubates out of the egg. It doesn't take care of and consequently has just 3 hours of endurance during which it needs to swim about looking for a reasonable base for connection. The hatchling needs progressed highlights for its free-swimming presence, which is so essential for dispersal of the populace to inaccessible spots which the stationary grown-up has no way to do.