Which sentence correctly forms the plural of the letter r? A. I wrote extra r's at the end of roarrr to show the sound the lion made. B. I wrote extra rs' at the end of roarrr to show the sound the lion made. C. I wrote extra rs at the end of roarrr to show the sound the lion made.
"I wrote extra r's at the end of roarrr to show the sound the lion made" is the sentence that correctly forms the plural of the letter "r". This is almost always done with apostrophes.