When comparing capacity-to-capacity， the IBM Rear Door Heat eXchanger helps provide more advantages than other available thermal environment solutions， usually at a fraction of the cost.   Which of the following statements is NOT an advantage of the IBM Rear Door Heat eXchanger？ （）

• A、The IBM Rear Door Heat eXchanger may dramatically unburden existing AC units by cooling the air before it exhausts from the electronics into the hot aisle.
• B、The IBM Rear Door Heat eXchanger is a "hang， plug， and run" design so the units may be added quickly.
• C、The IBM Rear Door Heat eXchanger is equipped with two fans to help maintain water temperature at 18C （64.4F） and provide even air flow.
• D、The IBM Rear Door Heat eXchanger is designed to support a 42U rack.