<span>Stem-changing verbs in the preterite normally change o —> ue or e —> ie.</span>
Explain how to do this, are you converting it to english or sumn?
Answer:
El correo el postal siempre lleva lugar, fecha y firma del emisor a diferencia del correo electrónico. Los correos postales no son públicos.
Vivir is the verb meaning "to live."
a through c are different tenses of vivi. To live is not a command nor is there a formal/informal way to say it.
vivimos - We live
viven : They live
vive : She lives