Which of the following animals is without a sexual medusa stage?

The poisonous substance present in the cnidoblasts of Hydra is:

Identify the correct features for $Medusa$ and $Polyp$ forms in Phylum $Coelenterata$ (Cnidaria) from the given list:
$I$ - $Sessile$
$II$ - $Umbrella-shaped$
$III$ - $Free-swimming$
$IV$ - $Produced$ $by$ $asexual$ $reproduction$
$V$ - $Cylindrical$
$VI$ - $Produced$ $by$ $sexual$ $reproduction$
$Medusa$ $\quad\quad$ $Polyp$

Radial symmetry is observed in:

Polyp phase is absent in $....$

Which of the following is a member of the phylum $Coelenterata$ (also known as $Cnidaria$)?