The fan in my laptop won’t stop running!

A client has brought you laptop that was purchased 14 months ago. Although the laptop worked normally for most of that time, the fan inside of the laptop has recently started running constantly at a very high speed. The fan works normally during the first few minutes after powering on, but it runs at full speed until the system is powered down. What is the most likely cause of this problem?

A) The fan settings in the BIOS have been modified

B) The cooling vents on the laptop are obstructed

C) The laptop requires a BIOS upgrade

D) The fan controller on the motherboard is faulty