下列塑料管道中,主要用于给水管道(非饮用水)、排水管道、雨水管道的是()。
A. 硬聚氯乙烯(PVC—U)管
B. 氯化聚氯乙烯(PVC—C)管
C. 无规共聚聚丙烯(PP—R)管
D. 丁烯(PB)管
屋面卷材防水施工中,叠层铺贴的各层卷材,在天沟与屋面的交接处,应采用()搭接。
A. 热粘法
B. 条粘法
C. 空铺法
D. 叉接法
Geothermal resources, wind turbines, and hydropower facilities in Paragraph 4 cited as examples to illustrate that __________. 查看材料
A. the amount of alternative energy production from public lands is huge
B. alternative energy production is no less than conventional energy production
C. they are the most typical conventional energy resources from public lands
D. geothermal resources are more important than the other two
钢结构构件焊接时产生气孔的主要原因,不包括()。
A. 焊条药皮损坏严重
B. 焊条和焊剂未烘烤
C. 焊接电流太大
D. 母材有油污或锈和氧化物