Plurals

Q. Is it the three R’s or Rs? The NYT seems to use R’s—I thought I’d double check with you folks before I publish something.

A. Either way is fine, but Chicago style is Rs. (The New York Times evidently prefers to follow NYT style.) Please see CMOS 7.15.

[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]