arghhhh I have just read a grammar book... I know, I know, I need to "get a life".
Anyhow - it says in there that to prevent confusion, it is perfectly acceptable to add in an apostrophe for clarity in a plural... as in "dotting the i's and crossing the t's " and indeed, when I google search, it appears to be the case... are there any other plurals where you habitually put an apostrophe s...