声音的质量特征称为()。
A.音强
B.音高
C.音色
D.音波
参考答案:C
Sam ______ his homework in his room now.[ ]
A. does
B. doing
C. is doing
D. do
采用暖棚法时应遵守下列哪些规定()
A.暖棚应经设计并绑扎牢固
B.所用保温材料应具有阻燃特性
C.施工中应经常检查并备有必要的消防器材
D.地槽式暖棚的槽沟土壁应加固,以防冻土坍塌