Possible Duplicate: Past participle of a verb created from an acronym. Since RSVP has morphed into a verb, I was wondering the correct way of using its past tense. Which of the following is the correct way to use the past tense of RSVP?
1) Only 1 person RSVP'd to my event.
2) Only 1 person did RSVP to my event.
3) Only 1 person RSVPed to my event.
4) None of the above