Here’s the Answer to the Question posted on Facebook
Q. You boot up a computer and see the following error message: “OS not found.” What is the MOST likely problem?
A. The computer has a dual boot operating system.
B. The computer failed with a stop error.
C. The graphics card failed.
D. A USB drive is plugged in.
Answer available until November 11, 2015.
See Chapter 4 of the CompTIA A+ Training Kit (ISBN 978-0735662681) by Darril Gibson.