Which of the following is a correctly matched pair?

Identify the organism that is different from others based on the presence of a coelom.

Identify the correct terms for the following analogy-based questions:
$(i)$ Porifera : Choanocytes :: Platyhelminthes : ....
$(ii)$ Chondrichthyes : Placoid scales :: Osteichthyes : ....

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

Which of the following is common among a leech,a mosquito,a bed bug,and a rat?

Find the mismatched pair regarding the exoskeleton.