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 now “the three R’s” (a change instituted for the 18th edition of CMOS that aligns our style for the plurals of individual uppercase letters with our style for individual lowercase letters). Please see CMOS 7.15.