-Immediately , quickly
-Simultaneously , Together.
Use of "at once" in sentence.
- Police ordered to vacate the mall at once(Immediately) as a time bomb was found on the first floor of the mall.
- At once(Immediately) you leave this place before I cut your throat.
- At once(Simultaneously) we should all fight together to survive otherwise we all will die.
- The super computer can process many requests at once(Simultaneously).
Note: Make and post one sentence using phrase "at once". Show you have learned and ready to use this phrase.