Which sentence correctly forms the plural of the letter x?

A.

Is exaggerate spelled with one or two xs'?

B.

Is exaggerate spelled with one or two xs?

C.

Is exaggerate spelled with one or two x's?

The sentence the correctly forms the plural of the letter x is option C. Is exaggerate spelled with one or two x's? When writing the letter x in its plural form, the rule is to put an apostrophe before the letter s. This is too differentiate and mean that the letter x is in plural form because if it is not indicated with an apostrophe, "xs" may mean a different thing.