采暖主立管用管卡或托架安装在墙壁上，其间距为3~4m，主立管的下端要支撑在坚固的支架上。管卡和支架不能妨碍主立管的胀缩。
参考答案：对
如图水坝的下部总要比上部建造得宽一些，这是为什么？
While large numbers of residents in this area _____ the H1N1 flu, very few suffered death. [ ]
A. picked up
B. took up
C. brought up
D. caught up
