It could refer to the mirror or the shelf.
When it is unclear what the antecedent of a pronoun is, it's calleda pronoun-antecedent error.
a. clear The antecedent for the pronoun 'this' is easy to recognize as 'problem'.
"He was tired." (Antecedent: John) "She is a doctor." (Antecedent: Sarah) "They are going to the store." (Antecedent: the children) "It is raining." (Antecedent: the weather)
Antecedent
His could refer to Scott or Jim.
Antecedent.
I can assure you that your antecedent enjoyed no such privilege. This event has a colorful story regarding it's antecedent.
It is the pronoun's antecedent.
The word antecedent is a noun.
Pronoun: he Antecedent: John
Antecedent means coming before something else. Oral storytelling is the antecedent to modern fiction.
A pronoun that has the same gender and number as its antecedent is called pronoun-antecedent agreement.