Answers: C and D - The GPU and display cable should be tested to determine if they need to be replaced.
Key Takeaway: If the monitor works fine on another computer, it means that the monitor is a good-known one. The issue is with the display element on the PC, which indicates that testing is needed for the display cable and GPU. The only other display element on the PC is the VGA port, which is integrated to the motherboard. A VGA port cannot be replaced individually, so the entire motherboard would need to be replaced instead.