The correct answer is:
d. ...are often below the total cost, because they usually do not include shipping charges.
Rationale: Retail websites often list prices for products but may not include additional expenses such as shipping, taxes, or fees, which can increase the final cost. It’s common for customers to see a lower price listed before checkout and then discover additional charges that bring the total cost up. This makes option d the most accurate statement regarding the prices listed on retail websites.