all at once
1. 突然
【例句】
All at once there was a loud crash. 突然一声巨大的碰撞声。
2. 同时
【例句】
Three buses arrived all at once. 3辆公共汽车同时到达。
【注意】
all at once在句中的位置很自由，另外all和at once可以分开使用，比如Don't eat all your chocolates at once. 不要一下子把你的巧克力都吃完。
【Question 提问】
句型转换
All at once she was wakened by a loud crash.（保持句意不变，每格一词）
______ she was wakened by a loud crash.
答案：Suddenly