According to ancient records, the first tax that the government of Selea imposed on a basic commodity was a tax of two centima coins on every jar of cooking oil sold in Selea. Tax records show that despite a stable population and strict enforcement of tax laws, revenues from the oil tax declined steeply over the first two years that the tax was in effect. Which of the following, if true, most helps to explain the decline in Selean oil-tax revenues? ['Two years after implementing the tax on cooking oil, the Selean government began to implement taxes on numerous other basic commodities.', 'After the tax was imposed, Selean merchants began selling cooking oil in larger jars than before.', 'Jars of cooking oil were traditionally bought as wedding gifts in Selea at the time the tax went into effect, and gifts of cooking oil increased after the implementation of the tax.', 'Few Selean households began to produce their own cooking oil after the tax was imposed.']