The sales volume of a product last year was reduced by half compared to the previous year. A survey by the marketing department found that the biggest difference between last year and the previous year was that the price of the product increased by 20%. Which of the following measures are most likely to effectively address the decline in merchandise sales:. ['Using multiple media to strengthen advertising.', 'Add more functions to the product.', 'According to the actual situation, seasonal floating price of commodity prices.', 'Give the customer a small gift.']