答案：C
2010年南非世界杯足球赛场上，南非球迷有一种叫呜呜组啦的喇叭能发出高达130dB的声音，相当于喷气式飞机发出的声音强度，很多球迷到现场观看比赛时都配备了耳塞，这是为了防止_______进入人耳；这种喇叭能发出声音是由于喇叭内空气柱________产生的。
用所给单词的适当形式填空。
1. It's three thirty. Please stop _______ (work) and have a relax.
2. I'm _______ (stress) out because my English isn't improving.
3. It is snowing ________ (heavy) outside. Let's stay at home.
4. All the ________ (sing) are from Singapore.
5. What are the ________ (different) between the movies and the TV plays?
