答案：C

题目分析：句意：张先生在哪里？他已经离开两天了。我能给他留个信息吗？句中有for two days.表示一段时间，句子中谓语动词要有延续性，leave改为be away，故选C

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