A local bookstore experienced a 15% increase in online sales after redesigning its website to be more user-friendly and visually appealing. The owner concludes that the redesign directly caused the increase in online sales. Which of the following, if true, most strengthens the owner's conclusion?

The correct answer to the question "A local bookstore experienced a 15% increase in online sales after redesigning its website to be more user-friendly and visually appealing. The owner concludes that the redesign directly caused the increase in online sales. Which of the following, if true, most strengthens the owner's conclusion?" is Option B: No new marketing campaigns were launched by the bookstore during the period following the redesign..

The other options — A) The bookstore's in-store sales also increased by 5% during the same period., C) A competing online bookstore experienced a 10% decrease in sales during the same period., D) Customer surveys indicated that 60% of online shoppers preferred the old website design. — are incorrect for this GMAT Exam Prep question. As explained above: By ruling out an alternative cause (new marketing campaigns), this option strengthens the conclusion that the website redesign was the direct cause of the sales increase, as no other significant fact…