From the given options, select the Figure of Speech (Poetic Device) used in the expression:

The spur of ambition

Metaphor

The figure of speech used in the expression "The spur of ambition" is metaphor.

A metaphor is a figure of speech in which one thing is compared to another thing without using the words "like" or "as." In this case, the spur of a horse is being compared to the motivation of ambition. This creates a sense of the driving force that ambition can be.

The other answer choices are incorrect. Pun is a play on words. Simile is a comparison between two things using the words "like" or "as." Oxymoron is a figure of speech in which two contradictory terms are used together. None of these devices are used in the expression "The spur of ambition.".