Metameric segmentation is the characteristic of

How many classes are present in Gnathostomata?

Which of the following is a correctly matched pair?

$A$: Annelids and Arthropods exhibit bilateral symmetry.
$R$: In Annelids and Arthropods,the body can be divided into identical halves through any plane passing through the central axis.

Match the following columns correctly and select the appropriate option:

Column $A$	Column $B$	Column $C$
$(1)$ Planaria	$(a)$ Planula	$(e)$ Ostia
$(2)$ Hyalonema	$(b)$ Pseudocoelomate	$(f)$ Flame cells
$(3)$ Hydra	$(c)$ Platyhelminthes	$(g)$ Polyp
$(4)$ Wuchereria	$(d)$ Porifera	$(h)$ Aschelminthes

In which one of the following is the genus name,its two characters,and its class/phylum correctly matched?

Genus Name	Two Characters $\&$ Class/Phylum
$A$. $Ascaris$	$(i)$ Body segmented,$(ii)$ Males and females distinct; Phylum: $Annelida$
$B$. $Salamandra$	$(i)$ $A$ tympanum represents ear,$(ii)$ Fertilization is external; Class: $Amphibia$
$C$. $Pteropus$	$(i)$ Skin possesses hair,$(ii)$ Oviparous; Class: $Mammalia$
$D$. $Aurelia$	$(i)$ Cnidoblasts present,$(ii)$ Organ level of organization; Phylum: $Coelenterata$