Answer:
D) Object
Step-by-step explanation:
A pronoun is a word used instead of a noun. The pronoun 'its' is used to denote the possessive nature of the noun, 'object'. This implies that instead of repeating the word object, 'its' is rather used to denote that which belongs to or characterizes the object. In the sentence above, the object was the central subject being referred to. The material properties of the object affects the amount of light that it can absorb.
The index of refraction of this same object is another factor that affects the amount of light the object absorbs. Therefore, the pronoun, 'its', refers to the object being discussed.