The correct answer is: "its"
Explanation:
The textbook definition defines noun as a person, place or a thing. Everything that does not belong to a person category assumes to in a "thing" category (if not places). The pronoun we use for anything that is not a person is "it." Here in this case, "one of the horses" phrase is used. A horse does not lie in the person's category. Therefore, we will use "it." In the case of possessive pronoun, the possessive form of "it" is "its." Therefore, the correct answer in this case is "its."
Explanation:
the cycle of processes by which water circulates between the earth's oceans, atmosphere, and land, involving precipitation as rain and snow, drainage in streams and rivers, and return to the atmosphere by evaporation and transpiration
