Henry O. is a firm believer in capital market theory and the capital asset pricing model. Henry has developed a model to select overpriced stocks as indicated by the security market line. The model identifies the overpriced securities and then executes a short position in the overpriced stock. Which of the following practical conditions would prevent Henry from using his model to explain capital market behavior（）

A. All investors use exactly the same two-stage dividend discount model to evaluate stocks.  B. All investors pay the same commission rate of $ 0.03/share on all equity trades. 

C. All borrowing and lending is done at a rate equal to the return on a 6-month Treasury bill.