Answer:
C. Simile.
Step-by-step explanation:
Figures of speech are employed by an author to add beauty, lend texture and incorporate color to their writing. The figure of speech that is employed in the given sentence is simile in the phrase "as giddy as June bride". The phrase illustrates simile as it compares Aunt Rose to a June bride with the use of the word "as". A simile is purposefully employed to add emphasis and vivid details to the subject with the use of words like "as ", "like", etc. Thus, option C is the answer.