“How long did he stay here?”“About two hours.” “他在这儿呆了多久?”“大约两小时。” 2. how often 指每隔多久,主要用来对频度副词或状语(如once a week等)提问: How often does he come here? —Once a month. 他(每隔)多久来一次? —一每月一次。 How ofte...