From the given options, select the correct figure of speech (poetic device) used in the following expression-

The wise fool impressed the king

Oxymoron

The correct figure of speech used in the following expression "The wise fool impressed the king" is oxymoron.

An oxymoron is a figure of speech in which two contradictory terms are used together. In this case, the words "wise" and "fool" are contradictory terms. A fool is typically thought of as being someone who is foolish and ignorant, while wise is typically thought of as being someone who is intelligent and knowledgeable. The use of these two contradictory terms creates a sense of the fool's unconventional wisdom and the king's surprise.

The other answer choices are incorrect. Simile is a figure of speech in which two things are compared using the words "like" or "as." Metaphor is a figure of speech in which one thing is compared to another thing without using the words "like" or "as." Personification is a figure of speech in which inanimate objects are given human qualities. None of these devices are used in the expression "The wise fool impressed the king.".