CTU follows APA Style in determining things like font, double spacing, indentions - all the details on how a written work should appear.
APA 7th edition does not require a certain font. It says to use a font that is appropriate for the audience and the purpose of your writing - but be sure that one font is used consistently throughout the document. It lists fonts like Times New Roman or Calibri as good choices for most circumstances.
The APA Paper Template is in Calibri 11 point font because that was the default font in Microsoft Word when the template was created. Microsoft has since changed their default font to Aptos, which is also an acceptable font for academic writing.
If you want to use a different font, ask your instructor. They are your audience since they are the one grading the paper, so their opinion matters most.
