Explanation:

The correct answer is option: 2: 'DCBA'.

Explanation

The given question is an example of a Para Jumble.
We know that the first statement of a para jumbled question is usually an independent general statement, a noun, a universal fact, starting of an incident, or it starts with 'most' or 'once'.
Sentence D will be the first sentence because it is an independent general statement telling us about the cost of a product.
Sentence C will be the next sentence because it is connected with the previous sentence.
Sentence B will be the next sentence because it is talking about the retailer who plays an important link between the producer and the consumer.
Lastly, Sentence A will be used.
Thus, the correct sequence is:
D: The retailer determines the final cost of a product.
C: It is he who promotes or impedes the sale of products.
B: As the final link between the producer and the consumer, he plays a key role in the economy.
A: His role also includes the smooth flow of goods from farms and factories to the consumer.
 
Correct Sequence: The retailer determines the final cost of a product. It is he who promotes or impedes the sale of products. As the final link between the producer and the consumer, he plays a key role in the economy. His role also includes the smooth flow of goods from farms and factories to the consumer.