An insurance customer installs two BladeCenter chassis in a rack with glass doors. After a short time， the blowers in both BladeCenters increase to full speed， and then one fails. Apart from replacing the broken blower， which additional action is required for a long term fix of the following？（）

Add Rear Door HeateXchanger
B. Add fans to the top of the racks
C. Increase circulation from Data Center raised floor
D. Change to perforated door