The sentences that use a comma in a way that is considered contested usage are:
-
We are passing through New Orleans, Louisiana right before we stop in Houston, Texas. - The comma after "Louisiana" can be considered unnecessary in some style guides, such as AP style, which recommends omitting it if the state name is not in an address format.
-
Stephen did not understand the question, and so Gina tried to explain it to him more clearly. - The use of the comma before "and so" can be contested because "and so" is often considered a coordinating conjunction that may not require a preceding comma, especially in casual writing.
So, the correct answers are the third and fifth sentences.