答案：A

题目分析：句意：这部小说你已经看了多久了？三天。How long表示多长时间，要和表示延续性的动词连用，borrow需要改为keep,故选A

点评：非延续性动词向延续性动词的转变熟记一下几个：

leave --- be away,  borrow --- keep,   buy --- have,  begin/start --- be on,      die --- be dead, leave --- be away from, fall asleep --- be asleep