时间的标志词···我印象中都是一样的，比如since，for，till,until等等···给你举个例子：I have waited here since an hour ago.或者I have been waiting here since an hour ago.
现在完成进行时have been doing表示一直在做状态有可能还会继续做，而现在完成时have done是到现在已经做完。一搬根据语境判断！！
