Select the sentence that is punctuated correctly.
Ruby emailed her instructor, a question, and he replied to her immediately.
Ruby emailed her instructor a question, and he replied to her immediately.
Ruby emailed her instructor a question and he replied to her immediately.
2 answers
And you think it's ... ?
Just in case you are unclear on comma uses in American English, here's this webpage you can study:
http://owl.english.purdue.edu/owl/owlprint/607/
http://owl.english.purdue.edu/owl/owlprint/607/