If advertising succeeds in enhancing brand loyalty among consumers, it tends to enhance the monopoly power of the seller.

This statement is TRUE.

Explanation:

To enhace the monopoly power of a seller, means that one seller can monopolize or have more power over the market of certain products. What advertising does when succeeding is promoting one brand, generating consumers to buy only that same brand.

The consumer's loyalty generates the monopoly of the market, making consumers only choose this same brand. This is why advertising is so powerfull and afects directly on the economy.