Which of the following is the primary difference between the network structure of national LTL carriers relative to regional LTL carriers? Question 2 options: a) National LTL carriers rely more heavily on breakbulk facilities to consolidate and deconsolidate shipments. b) National LTL carriers rely more extensively on subcontractors for freight shipments. c) National LTL carriers have higher density of freight flowing on the lanes in their network. d) National LTL carriers specialize in hauling retail-oriented freight