posted by Cid .
when should you use commas or dashes to set off an appositive phrase
An appositive is a small section of extra information which is inserted into a sentence for clarification. Commas are usually used to offset the appositive, but if the appositive contains one or more commas, that would get confusing for the reader. When using an appositive that contains a comma, offset it with dashes, instead.
when it is not essential to understand the question
B. When it is not essential to understand the sentence.