A construction engineer is working on a hydroelectric dam project in South America. He travels to the construction site every month from his home in Colorado and uses a portable hard drive to transfer files he needs to work with when he is at the project site.

On his last trip, he had left the portable drive plugged into the desktop computer in the project office while he was out on the site. A severe thunderstorm struck, knocking out power on the site. When he was able to return to the office, he noticed the power indicators on the office computer and the portable drive were on, but he couldn't get anything to appear on the computer monitor.

What is the most likely source of the problem?

A. A power surge from the storm damaged the computer monitor.
B. A power surge from the storm erased the computer's operating system files.
C. A power surge from the storm damaged the power supply on the computer.
D. A power surge from the storm caused the portable hard drive to fail.