1、B   how often對(duì)表示頻度的副詞提問(wèn)；how long對(duì)一段時(shí)間提問(wèn)；how far對(duì)路程提問(wèn)；how soon對(duì)表示將來(lái)的某一段時(shí)間提問(wèn)。“For about two months．”表示的是一段時(shí)間，故選B。