答案：D

题目分析：句意：这本书我已经借了两周了，现在我必须归还它。borrow是非延续性动词，用于现在完成时态时不能和时间段连用。可用延续性动词keep代替borrow。

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