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(jué)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(guò)的香草聞起來(lái)既沖又香氣撲鼻。

　　All at once I fell into a state of profound melancholy.

　　我立即陷入無(wú)限的愁思之中。