$\text{Incorrect statements}$
$\text{Statement c:}$ Polyp produce medusae sexually and medusae form the polyp asexually (eg: Obelia).
$\text{Elaboration :}$
Obelia (Sea fur) belongs to the class Hydrozoa of the kingdom Cnidaria that shows polyp (cylindrical) as well as medusa (umbrella-shaped) form in its life cycle.
$\text{Statement d:}$ Metagenesis is seen in jellyfish.
$\text{Elaboration :}$
Cnidarians, which exhibit both the types of body forms, polyp (cylindrical) and medusa (umbrella-shaped), exhibit metagenesis. Aurelia (jelly-fish) only shows umbrella-shaped (medusa) form and therefore, does not exhibit metagenesis. Hence, statement ādā is incorrect.
$\text{Final answer}$
$d. ~c, d$