the planes had been planting seed for a month为什么这里seed 是单数

the planes had been planting seed for a month为什么这里seed 是单数 the planes had been planting seed for nearly month when it began to rain求翻译和解释 The planes had been planting seed for nearly a month whtn it began to rain.这句话中的when是什么用法,为什么用when引导而不用before. The planes had been planting seed for nearly a month when it began to rain.这里可不可以把when换成before,如果不能,为什么 The planes had been planting seed for nearly a month when it began to rain.had been planting 为甚么用过去完成进行时,如果用过去完成时可以吗 请分析这句英文语法布莱里奥从1905年起便开始研制飞机Bleriot had been making planes since 1905为什么不是Bleriot had made planes since 1905 What made the story hit close to home was that Bob Collins,the morning show man for WGN,was the pilot of one of the planes and had been killed Has it been been announced if the planes are to take off?这个句子对吗? the morning show man for WGN,was the pilot of one of the planes and had been killed.为什么was 前面要加一个逗号啊 是什么语法啊 英语翻译Bill was a very good pilot.He had been in the air force for several years,and had been very successful.Now he was sent to a small field in the middle of a forest,from which planes were able to attack the enemy very easily,for it was near 几句英语句子对比!1 He had been making planes since 1905 and this was his latest model2 The latest model of the plane which he had been making since 1905他从1905年起便开始研制飞机,飞机是他制作的最新型号3 He landed on the 英语求助Has it been announced when the planes are to take off求句子成分分析 新概念英语2册62课问题.1.firemen had been fighten the forest fire for nearly three weeks.意思是：消防员用了3个星期就火.帮我改成：消防员救完火后的3个星期.2.the planes had been planting seed for nearly a month.意 they had to change the planes ,() they A hadn't B didn't C did Has it been announced ——?A.when are the planes to take offB.that are the plans to take offC.where are the planes to take offD.when the planes ate to take off 求英语达人告诉我答案以及为什么选这个答案.要详细一点.Before the first non-stop flight was made in 1949,it_____necessary for all planes to land for refueling.A.would be B.has been.C.had been D.would have been The Attack had been the boundary,had I lost him The planes ___nearly a month to plant the seed.(a)did (b)made (c)took (d)had