B.Imagery
Imagery is the use of words to create a picture in the reader's mind. In the poem the speaker is describing how the fog comes and envelopes the city. Throughout the passage, the fog is compared to an animal with a muzzle that rubs against the windows. The images this creates shows how the fog silently invades and covers everything.
A hyperbole is an over exaggeration. An allusion is a reference to another published work. An understatement is a description that plays down the subject and makes it less than it is.