<em>"Evil air, a frost-making stillness" is an example of </em><em>a. metaphor.</em>
Explanation:
A metaphor is a literary device used to describe an action or object in a way that is not really true or literal by introducing an implied comparison. This figure of speech defines an object or idea -in this case <em>air </em>and <em>stillness</em>- by suggesting a likeness or analogy with another -<em>evil </em>and <em>frost-making</em>- that are usually unrelated.