What is the scientific study of fishes called?

In the given examples,how many animals are viviparous? Corvus,Columba,Macropus,Pteropus,Calotes,Hemidactylus,Psittacula,Struthio and Macaca.

Match the following genera with their respective phylum:

$(a)$ Ophiura	$(i)$ Mollusca
$(b)$ Physalia	$(ii)$ Platyhelminthes
$(c)$ Pinctada	$(iii)$ Echinodermata
$(d)$ Planaria	$(iv)$ Coelenterata

Select the correct option:

Which of the following are correctly matched with respect to their taxonomic classification?

Which of the following is observed in the adult stage of $Cnidaria$ and $Echinodermata$?

Assertion $A$: Fishes possess gills,fins,and scales.
Reason $R$: Fishes are a form of taxon.
Which option is correct for Assertion $A$ and Reason $R$?