突然，我们听到了一声响亮的敲门声。

___All ___of ___a ___sudden we heard a loud knock on the door.

突然，一个奇怪的生物出现在他的梦中。

___All ___of ___a ___sudden, a weird creature popped into his dream.

突然，停电了。

___All ___of ___a ___sudden, the power went out.