有关对燃气管道安装的要求中，居民用气设备的烟道距易燃的顶棚或墙的净距不应小于（）cm。
A．10
B．20
C．25
D．30
参考答案：D
某面积较小的岛国为改变淡水供给不足的状况，规划在填海地段建地下水库──将收集的雨水和地表径流，通过灌注井储存于地下含水层，需要时回抽补充地面供水。据此回答29～30题。
提出此项规划，是因为该国：（）
A.火山活动频繁
B.降水丰富
C.干旱少雨
D.污染严重
As technological advances put more and more time between early school life and the young person’s final access to specialized work, the stage of______becomes an even more markedand conscious period.
A. adolescence B. adjacency C. advantage D. adventure
