The approach used when the marketer wants the consumer to respond on an emotional, rather than rational basis:

Answer: Option C

The approach where marketers aim to evoke an emotional response from consumers rather than a purely rational one is known as Psychological Pricing. This strategy often involves setting prices that end in certain digits, like $9.99insteadof$10.00, to create a perception of a lower price and encourage emotional buying decisions.

Option A: Predatory Pricing is a strategy where a company sets very low prices to drive competitors out of the market, which is not related to emotional responses.

Option B: Economy Pricing is focused on offering products at low prices based on cost efficiency, not emotional responses.

Option D: Penetration Pricing is used to gain market share by setting initially low prices, but it's not primarily aimed at emotional responses.

So, the correct answer is Option C: Psychological Pricing, as it targets emotional responses in consumers through pricing strategies.