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.