The correct option is D Personification
'Personification' is a literary device / figure of speech in which an inanimate object is given human attributes or characteristics. In simpler terms, a personification occurs when something that is not human is treated as such. In this case, the speaker's diary has been treated as a person, to whom she whispers her secrets. Thus, the correct answer is Option D) - Personification. All the remaining options are also literary devices, but they have not been used in the given sentence.