Fill in the blanks with a suitable option:
When Mary said to the dog, "Stop wagging your tail", ______ started wagging ______ tail faster.

The correct option is C it, its
Here, the sentence talks about Mary and her dog. The pronoun used for an animal when the gender is not known is 'it' and 'its'. So, the correct answer is option C).

Option A) 'you, your' are used as personal second person pronouns and cannot be used here. Option B) 'she, hers' is used to refer to a third person female and is incorrect in the given context. Option D) 'they, their' is third person pronoun used for a group of people and is also incorrect.