Which of the following is correct for the phylum that exhibits bioluminescence?

In Ctenophora,the body bears $....$ external rows of ciliated comb plates,which help in locomotion.

Why is $Ctenophora$ considered a minor phylum?

Define/Explain: Bioluminescence.

Bioluminescence is a characteristic of which phylum?

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.