Which group of animals possesses a $U$-shaped digestive tract?

What is the larval form of Hemichordata called?

Which of the following characteristics applies to $Balanoglossus$?

Which of the following organisms has the smallest sperm?

The phylum which was earlier considered as a sub-phylum under $Chordata$ but now placed as a separate phylum in non-chordates is:

Which of the following is a common feature shared by Hemichordata and Chordata?