虚拟传真在发送传真时，如对方是人工应答，系统可以自动播放（）提示，请求对方接收传真，从而提高了传真的成功率。
参考答案：语音
燃烧炉系统主要包括：燃烧炉、（）、热风管路、柴油泵、油、气管路、阀门组架。
It's raining hard. Peter's mother him at home. [ ]
A. worry about
B. worried about
C. worrying about
D. is worrying about
