----will the library be completed?-----six months how long w

how soon in How soon 问多久,意思是图书馆还要多久才能竣工。以How soon 提问的句子回答一般用in加时间段。e。g:____How soon will he be back?____In three days。How long是问时间多久或东西多长。若问时间的话一般与延续性动词连用。答语一般是for加时间段或 since加时间点,或since后加一般过去式的句子。1。___How long have you stayed in China?___Since I was seven。/ For eight years。2。___How long is the ruler?____It's twenty centimeters。