travel过去式是traveled还是travelled,

是travelling还是traveling?是travelled还是traveled? （闭音节）像travel这种重读不在的vel,可以为travelled,也可以是traveled也是什么意思, traveled和travelled到底哪个对 travel的过去式是啥. 是traveling 还是travel travel的过去式? “travel”的过去式 是travel agent's office还是travel agents' office 旅行社的英文翻译是Travel Agency还是TRAVEL SERVICE? 是travel to vacation,还是travel on vacation 长途旅行是travel long distance 还是 travel long distances? He traveled to work 这句话中的travel是什么意思.