All at once there was someone knocking on the door.
忽然有人敲門。
She wanted to laugh and weep all at once
她哭笑不得。
I feel terribly sleepy all at once
我突然覺得特別困。
In the hot sun the rain-washed herbs smelled sharp and spicy and sweet all at once.
烈日下，被雨水沖刷過的香草聞起來既衝又香氣撲鼻。
All at once I fell into a state of profound melancholy.
我立即陷入無限的愁思之中。