Answer:
The appositive in the sentence above is "Mrs. Eddy" (A).
Step-by-step explanation:
An appositive is a noun or noun phrase that renames another noun right beside it. In the sentence above, the appositive is the NP "Mrs. Eddy" and it renames the NP "our neighbor". What is more, the appositive phrase is nonessential since the information it provides is not considered relevant to complete the meaning of the sentence. If it was dropped, the meaning would be left unchanged (1). That is why it is offset with commas.
1) Our neighbor is an editor