plzz explain me d sol

Dear student

 (a) is petromyzon a member of cyclostomata 
(b) is scoliodon a member of chondrichthyes
(c) is salamandra a member of amphibia
(d) is ornithorynchus a mammal

Chondrichthyes have internal fertilization, hence your given solution is wrong as you have to choose the correct one.
Anamniotes are organisms which lay there eggs in water(they are lower vertebrates), this group comprise mainly fishes and amphibians
hence (b) is a fish and (c) is an amphibian.
option (c) is correct.

regards