The students are sorry to hear that the famous singer______(be) away for half an hour.是填has been 还是will be ? has been应该好些吧?

应该填has been
for + 时间段 一般用于完成时
The students are sorry to hear that the famous singer has been away for half an hour.
学生们听说那个著名歌手已经离开半个小时感到很遗憾

肯定是has been，
要用will be 的话，后面的时间状语要改成in half an hour，将来时中的"...以后"用in＋一段时间

The students are sorry to hear that the famous singer has been away for half an hour.
学生们很难过听到那个有名的歌手半小时前已经离开了。
现在完成时，表示已经做完的事情，并对现在有影响。

应该是has been，如果是will be后面应该是half an hour later 而不是for half an hour

will be
以后离开才伤心, 已经离开伤心什么
学生们很难过听到那个有名的歌手会离开半小时

窃以为has been，现在分词，动作影响到现在，已经迟到并且现在还没来

has been
I think

呵呵,大概两个都可以吧!如果没有上下文的话,两个答案都应该没有什么语法问题!

学生很伤心地听到了那个著名的歌手在半个小时前走了.
是WILL BE吧