Final answer:
The answer is D) samples, as they allow consumers to try a new product directly, which encourages future purchases, but producing and distributing free samples is also the most costly promotional method.
Step-by-step explanation:
The most effective but most expensive consumer-promotion tool to introduce a new product is D) samples. Providing samples allows consumers to directly experience the product at no initial cost, which can encourage future sales. However, the cost of producing and distributing free products can be quite high, making it a costly promotional method.
In comparison, coupons offer a discount on the purchase price, which can stimulate sales but may not be as effective in reaching consumers who have not tried the product before. Price packs provide a value offer, such as two for the price of one, but also may not tempt new consumers who are unsure about the product's value. Contests can generate interest and excitement but do not guarantee that consumers will try the product.