Question

Which sentence correctly forms the plural of the letter s? A. How many s's are in Mississippi? B. How many ss are in Mississippi? C. How many ss' are in Mississippi?

Answer 1

The correct answer is A. When talking about more than one letter, the s needs to have an apostrophe in the middle of both letters.

Answer 2

In this case it would be 's

A. How many s's are in Mississippi?

The rule is use an apostrophe s to form plural of single letters.

Hope this helps.