In $2010,$ three top B$2$B $$ were Thermo Scientific lab and research supplies $($ $$10\mathrm{.}8$ billion$)$; Henry Schien dental, medical, and vet supplies $($ $$7\mathrm{.}5$ billion$)$; and WESCO International electrical and industry maintenance supplies $($ $$5\mathrm{.}0$ billion$).$

A$.$ catalog sellers

B$.$ inbound telemarketers

C$.$ mobile marketers

D$.$ outbound telemarketers

E$.$ infomercial marketers