If a tax is imposed upon a good that is produced and traded in a perfectly competitive market, then:

In a perfectly competitive market, when a tax is imposed on a good, the entire market structure is affected. The burden of the tax, which is the amount that consumers pay in higher prices and the amount that producers receive less due to the tax, leads to a decrease in overall welfare.

Consumers will be faced with higher prices as the suppliers pass on some of the tax burden, while producers will receive lower prices for their goods after the tax is taken into account. This situation typically results in a decrease in the quantity of the good traded in the market, leading to a loss of efficiency and a deadweight loss.

Additionally, the overall consumption and production decrease, meaning both buyers and sellers end up worse off compared to the equilibrium situation without the tax. This diminished trade volume represents a reduction in total surplus in the market, which aligns with the economic principle that taxes can create distortions in a competitive market.

In contrast to the options suggesting benefits or unchanged equilibrium, the reality of the situation shows the negative implications for both consumers and producers, thereby validating that both groups are indeed worse off after the imposition of the tax.