Select the option that is related to the fifth word in the same way as the second word is related to the first word and the fourth word is related to the third word. (The words must be considered as meaningful English words and must NOT be related to each other based on the number of letters/number of consonants/vowels in the word)

Elephant : Trunk :: Fish : Gill :: Kangaroo : ?

Pouch

The logic followed here is:

Elephant : Trunk

Trunk is an internal organs that are the extended nose of Elephant,

Fish : Gill

Gills are the internal organs that allow Fish to breathe underwater.

Similarly, for Kangaroo : ?

Pouch is the internal organs of Kangaroo that functions exclusively as baby containers.

Pouch is correct answer.