at noce/all at once We'ss o the work at once.我们立刻就干这项工作。 All at once I knew what to do.突然,我知道该怎么办了。 <辨析>at once 意为“立即”、“马上”(=immediately);all at once 意为“突然”(=suddenly),还可作“同时”、“一起”解。如:It is impossible to solve these porblems all at once.We'll take one at a time.我们不可能同时解决这些问题,而只能一个一个地解决。