correctly dotting the "i"s and crossing the "t"s in the expression "dotting the i's and crossing the t's" [duplicate]

I've found questions here at ELU related to the meaning of the expression (I'm clear on that), but this is about the best way to punctuate the expression in the title. Possibilities:

a. It's almost ready. I just need to go through it once more to dot the "i"s and cross the "t"s.

b. It's almost ready. I just need to go through it once more to dot the i's and cross the t's.

c. It's almost ready. I just need to go through it once more to dot the is and cross the ts.

a. shows what I would naturally do.

b. shows what appears to be most common (used in posts on this site as well as in Wikipedia), but it using that apostrophe for plural sticks in my craw. I did find some support for this, here, but this also suggests using the apostrophe for letter grades (see c. below).

c. seems terribly confusing, although it follows the convention of pluralizing letter grades (which are not so confusing because they are capitalized).

So... which is it?

Solution 1:

Apostrophes were once used in a lot of plural cases (I've said more on this here) and while some such cases are now completely obsolete, some are still used to varying degrees.

The case of pluralising a single letter is perhaps the strongest survivor of the pluralising apostrophe (and indeed even in the case of pluralising letter grades, as despite your claim one can indeed find "She got five A’s and two B’s" and similar uses today*). It avoids a tendency to consider the forms ts as a word and even more so is, since there of course is already a word is. (Also the English words as and us and abbreviations like vs).

So, considering that apostrophes for plurals perhaps shouldn't stick in your craw quite as much as it does, (i.e. fine as a personal preference, but not "incorrect"), and considering the various points you've made, there's no perfect answer as to "which is it?" and all three are found in different styles of correct contemporary use.

I'd add the possibility of italicising the letter:

I just need to go through it once more to dot the is and cross the ts.

Which is my personal preference when markup is possible, but not the sole "correct" choice, either.

*Though there are style-guides that are half-way between the two, in that they require plurals of capitals to have no apostrophe but plurals of lower-case letters to have an apostrophe, and so would have "Taking care to dot the i's and cross the t's meant she got As in all her exams".