Answer: A) It's.
Explanation: an adjective is a word that describes or modify a noun or a pronoun. A possessive adjective refers to a word which modify a noun (or pronoun) by showing a form of possession or a sense of belonging to a particular person or thing. In the given sentence we can see an example of a possessive adjective in the word "it's" because the "-'s" is modifying the pronoun "it" to indicate belonging.