Based on the descriptions below of different jobs Nancy has held, which would qualify as an oligopoly?

• Nancy wasa telemarketer for a software company with many buyers and sellers. Everyone's products were fairly unique, but it was very easy to enter the software market. One advantage Nancy's company had was that it had an informational advantage over many other companies.
• Nancy was a fruit vendor. In her market there were many buyers and sellers. It was easy and cheap to start a vendor stand. Everyone's fruits were basically identical.
• Nancy was a customer service representative for the local water company. The company had exclusive rights to operate as the only company providing water to local residents since the costs to lay competing pipelines were a barrier to entry preventing competition. They were, however, regulated by the government.
• Nancy was an administrative assistantfor an oil company with very few other sellers. Other companies had trouble getting into the fossil fuel market. All the fossil fuel companies had the same information, but they had an information advantage over the buyers.