beforeyesterday是什么时态的标志答:标志:ago,yesterday,theday before yesterday,last week(year,night,month…),in 1999,just now,at the age of 5,one day,long long ago,once upon a time,etc.结构:①be动词;②行为动词 三、现在进行时:标志:now,at this time,these days,etc.结构:am/is/are+doing 四、过去进行时:...