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
生物多样性面临的威胁主要体现为______的速度加快．
Woman: Are you prepared for the exam tomorrow
Man: Oh, yeah, the exam will be a piece of cake.
Question: What does the man mean().
A. The woman should take the exam.
B. The woman shouldn’t be concerned.
C. He is not worried about the exam.
D. He enjoys taking exams.
