Bonus Edna St. Vincent Millay Quiz by StevensDN

Question 1

One well known Millay sonnet begins this way:

What lips my lips have kissed, and where, and why,
I have forgotten, and what arms have lain
Under my head till morning…

Her use of “lips” and “arms” as a stand-in for the narrator’s lovers arguably employs what literary device, in which a part is used to represent the whole?