B2B stands for business-to-business commerce and implies that both sides of the transaction are businesses, nonprofit organizations, or governments. An example would be an AllState insurance agency buying computers from Dell. The transaction is between the two businesses (AllState and Dell) and the computers would be used to conduct business at AllState.
B2C stands for business-to-consumer and implies e-commerce transactions in which buyers are individual consumers. You can the same example as above (Dell ...
This solution "spells out" the abbreviations and gives at least one example for each one. It also gives you hints for tricky true/false questions that might fall into a gray area.