The correct answer to this question is font size 12. For those in school or doing assignments for work, it is second nature to use this font size, because nine times out of ten, this is what the professor or a boss will require the work to be completed as.
Along with the font size being 12, the standard accepted type of font is Times New Roman. The font size 12 is standard for many reasons. One reason is that it is easier to read. Going above or below this number can cause the font to be too small or too large when printed. Another reason is that it is easier to provide feedback on the page with this font.