A technician is experiencing overheating on a rack mounted server. After powering off and removing the cover of the server, a large amount of dust is noticed on one of the fans. After cleaning out the dust and powering the server back on, the server is still overheating. Which of the following would BEST explain this issue?
A. The power supply has failed.
B. The server is using excessive power.
C. The hard drives are running too hot.
D. Some of the cooling fans are defective.