Which of the following display retrogressive metamorphosis?
a)	Salpa and Herdmania	b)	Doliolum and Oikopleura
c)	Pyrosoma	d)	All of these

(d)

Metamorphosis is a charge from juvenile to adult stage in which larval stage is quite different from adult stage. In retrogressive metamorphosis, the larva possesess advanced characters which are lost during the development and adult is either sedentary or degenerated with primitive characters. All urochordates display retrogressive metamorphosis