In aquatic mammals

What are the adaptations shown by aquatic mammals in polar regions ?

Which among these is the correct combination of aquatic mammals ?

Sea cows are aquatic mammals included under

Assertion:- The aquatic mammals like Dolphins whales etc. do not contain gill slits. Reason : Their adaptation to aquatic life is secondary.

Assertion :- The aquatic mammals like Dolphins whales etc. do not contain gill slits. Reason : Their adaptation to aquatic life secondary.

Identify the aquatic mammals from following (i) Balaenoptera (ii) Equus (iii) Delphinus (iv) Pteropus (v) Felis

Identify the aquatic mammal(s) from the following (i) Balaenoptera (ii) Equus (iii) Delphinus (iv) Pteropus (v) Felis