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

The light of knowledge

Metaphor

The figure of speech used in the expression "The light of knowledge" 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 abstract concept of knowledge is being compared to a physical thing, such as light. This creates a sense of the illumination and enlightenment that knowledge can bring.

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