Final answer:
Psychological pricing is a strategy used by businesses to manipulate consumer perception of prices. The best example of psychological pricing among the given options is $9.99.
Step-by-step explanation:
Psychological pricing is a strategy used by businesses to manipulate consumer perception of prices. It involves setting prices that give the illusion of a better deal or value, even if the actual difference is small. In the given options, the best example of psychological pricing is option 4) $9.99. This price is just slightly below $10, which is a common reference point for consumers. By using $9.99 instead of $10, businesses tap into the psychological tendency for consumers to perceive the price as significantly lower.