On windows:
1. Right-click on an empty section of your Windows desktop.
2. Click the "Screen Resolution" option that appears in the list.
3. View the numbers shown next to the "Resolution:" heading on this screen. The first number is the number of horizontal pixels Windows is trying to display. The second number is the number of vertical pixels. If you see a "(Recommended)" label after this number, it is because Windows believes this screen resolution is the best one available to match your monitor or display.
mac: Click on Apple icon on left top.
About This Mac --> More Info... --> Display
You should see the resolution there.
iphone: http://www.whatismyscreenresolution.com/
android: same as iphone
Answer: BEDMAS
Explanation:
for business teachings its BEDMAS
Only B and C would be the best choice