The rhetorical device used in the sentence “o books who alone are liberal and free, who give to all who ask of you and enfranchise all who serve you faithfully! ” is
a. hyperbole
b. simile
c. apostrophe
d. litotes

C. Apostrophe

Explanation:

Apostrophe:

Apostrophe is a figure of speech by using which a writer or speaker addresses an absent/dead person as if he/she were present, or an inanimate object or idea as if it were a living thing and listening to him/her (speaker).

Examples:  

"O wild West Wind"

"O, my cell phone, you were so dear to me."

Hyperbole: It is an exaggerated statement not to be taken literally.

Examples:

"The sun came just meters away from the earth."

"She would conquer the entire universe with her smile"

Simile:

It is a figure of speech in which the writer makes comparison between two things which may have some relation but are different. Simile always uses comparison words such as, like, as, similar to etc.

Examples:

"He is as brave as a lion"

"Life is like a dream"

Litotes:

It is an understatement in which a positive statement is made by negating its opposite. Or use of double negatives to make a positive statement.

Examples:

"It was not one of my best days" to mean It was one of my bad days."

"The books was not bad" to mean the book was good."

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