Caesura is a pause or break within a line of poetry, usually placed for rhythmical effect. In the lines provided from Edgar Allan Poe's "The Raven," the first line contains a clear example of caesura:
“Once upon a midnight dreary, while I pondered, weak and weary,”
The pause occurs after "dreary," creating a natural break in the flow of the line.
Therefore, the correct response is: “Once upon a midnight dreary, while I pondered, weak and weary,”