Final answer:
The lowest-cost freight to ship according to NMFC codes is Class 50, as it includes items that are dense, easy to handle, and have a lower risk of damage.
Step-by-step explanation:
The National Motor Freight Classification (NMFC) code that represents the lowest-cost freight to ship is a) Class 50.
The NMFC system classifies freight based on four factors: density, stowability, handling, and liability. Class 50 freight is typically the least expensive because it usually consists of items that are higher in density and easier to handle, decreasing the risk of damage and theft during transport, which reduces costs for shippers.