In which of the following arenas would Walmart's Sam's Club stores compete against their closest, most intense rivals?

A、Theretailingsector;
B、Thediscountretailingindustry;
C、Theclub-storediscountretailingstrategicgroup;
D、Sam'sClubstoresfacenoclose,intenserivals.;
E、Sam'sClubstoresfaceclose,intenserivalsineveryarenainwhichtheycompete.