请问B选项错在哪里？

问题如下：

A risk consultant is giving a presentation to a group of analysts on the topic of subprime mortgages and how they contributed to the 2007–2009 financial crisis. The consultant begins the presentation by providing an introductory overview describing the mechanics of subprime mortgages as well as some subprime market trends that occurred in the years leading up to the crisis. Which of the following statements would be correct for the risk consultant to include in the presentation?

选项：

A.

While housing prices were rising, subprime borrowers would typically refinance adjustable-rate mortgages into another similar mortgage as soon as the teaser rate period ended

B.

By securitizing subprime mortgages, banks created pools of assets that were mostly rated below investment-grade to sell to investors

C.

The growth in demand for subprime mortgage financing leading up to the crisis was fueled in part by high interest rates and a strong housing market

D.

Based on the originate-to-distribute (OTD) model for subprime mortgages, the bank that initiated the mortgage loans incurred all the losses on the loans

解释：

A is correct. Some borrowers used subprime lending to purchase a house in which they intended to live, whereas others were merely speculating on rising home prices. For either type of borrower, an adjustable-rate loan could typically be refinanced into another similar mortgage once the teaser rate period ended (as long as housing prices rose).

B is incorrect. By securitizing subprime mortgages, banks created pools of mortgage assets that were originally speculative-grade, separated them into tranches based on the certainty of their cash flows, and packaged the safest cash flows as investment-grade assets to sell to investors. Typically, the tranches consisted of mostly investment-grade senior tranches (these often received an AAA rating) and mezzanine tranches, with only a small equity tranche that might be rated below investment grade.

C is incorrect. Growth in housing demand and the associated mortgage financing was fueled (in part) by the low interest rate environment that existed in the early 2000s.

D is incorrect. Under the OTD model, losses on subprime mortgages were borne not by the banks that initially made the loans, but by the investors that eventually owned them.