After Offering a Promotional Allowance,the Price of a Product Returns

After offering a promotional allowance,the price of a product returns to its regular price level.When this happens,the retail store's gross margin on that product __________ on those items that were bought with the allowance but not sold during the special price promotion.

A) decreases substantially
B) increases substantially
C) remains the same
D) fluctuates wildly
E) vanishes