人体组织和体液中，下列哪一项最能使声衰减程度加重
A．胆汁、尿液、血液
B．皮下脂肪
C．肝肾实质、肌肉
D．胶原纤维
E．钙质
参考答案：E
_____________ play on the street! It's dangerous. [ ]
A. Don't
B. Not
C. Please
D. No
