In discussing Mary Shelley's 1818 epistolary novel Frankenstein, literary theorist Gayatri Spivak directs the reader's attention to the character of Margaret Saville. As Spivak points out, Saville is not the protagonist of Shelley's ________ as the recipient of the letters that frame the book's narrative, she's the "occasion" of it.

Which choice completes the text so that it conforms to the conventions of Standard English?