Answer:
The correct answer is option A) its.
Step-by-step explanation:
Possessive adjectives are commonly defined as words that modify a noun or a pronoun, specifically showing who or what owns something or someone. There is a possessive adjective to correspond to each personal pronoun. They include my, your, his, her, its, our, and their.
Since they are adjective, they are always located in front of the noun they refer to.
Bearing in mind the explained above, it could be said that the pronoun that correctly completes the sentence provided is its. Resulting as follows:
In the top of the maple tree, the sparrow was busy building its nest.