Why is $Ctenophora$ considered a minor phylum?

What is the function of the comb plates present in Ctenophora?

Identify the phylum which shows the following characteristics:
$1$. Animals are exclusively marine,radially symmetrical,and diploblastic.
$2$. Body bears eight external rows of ciliated comb plates which help in locomotion.
$3$. Digestion is both extracellular and intracellular.
$4$. Reproduction is only by sexual means.

Which one of the following groups of animals reproduces only by sexual means?

Bilateral symmetry and the absence of cells are characteristics of which of the following?

Explain: $Ctenophora$.