Which of these descriptions best defines the term "metaphysical conceit"?
a. presenting conceited views of oneself in poetry
b. use of multiple figures of speech in a single line
c. unusual comparisons to describe commonplace things
d. an idealization of platonic love instead of physical love e. a jarring mixture of the hyperbole and synecdoche techniques

The description that best defines the term metaphysical conceit would be unusual comparisons to describe commonplace things.
For example, John Donne wrote a poem called The Flea in which he is talking about a mere insect on the surface level, whereas in fact he is using metaphysical conceit to talk about a romantic intercourse through the metaphor of a flee.