What type of muscles are present in the body wall of animals belonging to the phylum $Annelida$?

Which of the following is an example of the class $Polychaeta$?

Open vascular system is absent in

Larval stages are absent in the life cycle of . . . . . . .

Assertion $A$: Metameric segmentation is observed in Annelids.
Reason $R$: The body of an Annelid is divided into two equal halves by a single axis.
Which option is correct for Assertion $A$ and Reason $R$?

Which of the following animals does $not$ undergo metamorphosis?