The correct option is
B BalanoglossusAcorn worm is an any of the soft-bodied invertebrate belonging to phylum Hemichordata.
A) Doliolum is a urochordate.
B) Salpa is a urochordate.
C) Balanoglossus is another name for acorn worm.
D) Rhabdopleura is hemichordates but are not acorn worms.
So, the answer is ' Balanoglossus'.