吸声措施的主要作用是
A．控制噪声源传出声波强度
B．封闭噪声源
C．控制空气扰动
D．吸收声能，降低噪声强度
E．以上都不是
参考答案：D
Think and write. 写出下列单词的同类词。
1. apple:
2. pop:
3. pizza:
_______, a learned man makes fewer mistakes in life than a man without knowledge.
A．In general
B． As general
C． On general
D．At general
