Questions 21 to 25 are based on the following passage about 10 million people in the US alone from troops returning from war to students with music blasting through headphones are suffering from impairing noise induced hearing loss.

问题 21 到 25 基于以下段落，仅在美国就有大约 1000 万人，从战争归来的军队到通过耳机播放音乐的学生，正遭受由噪音引起的听力损失。