Final answer:
Barter is the oldest and least complex form of countertrade, involving a direct exchange of goods or services without money(option 1).
Step-by-step explanation:
Among the forms of countertrade provided in the options,1) barter is considered the oldest and least complex form. Barter involves a direct exchange of goods or services without the use of a medium of exchange like money. It predates other forms of trade and is based on mutual benefit between parties. In history, this type of trade is seen when, for instance, chickens were exchanged for newspapers. One party had something that the other party desired, and they would make an exchange to satisfy each other's needs.
Other forms of countertrade such as offset, switch trading, and buyback are more complex and involve more sophisticated trade agreements that often include future contracts or financial considerations, which can be more complicated than the simple exchange of goods and services seen in barter.