Answer:
A). Using "oyster shells" to give a sense of a restaurant.
Step-by-step explanation:
In rhetorics, metonymy is described as the figure of speech in which the poet employs a single characteristic or part of an object, concept, or phenomenon to identify the entire concept, object, phenomenon, or related object.
As per the question, the first option most aptly exemplifies 'metonymy' as it employs 'oyster shells' which is a part of the restaurant(used to serve oysters as the appetizer) to give the essence of the entire restaurant. The other options do not employ a part to convey the whole and hence, option A is the correct answer.