Answer is (B) to increase the demand for the product.
It is common to see stores and clothing outlets put up a sale banner outside their shops. There are two reasons behind it:
a. The product is new and needs to catch the attention of the buyers.
b. The product is old, not fetching any profits due to less demand among the buyers.
(a.) is strictly for promotional purposes and (b.) for the clearing of stock in shops to make way for new products. Both have a common purpose of increasing the demand for the product.