城市用地竖向工程设施的技术规定,挡土墙适宜的经济高度为1.5~3.0m,一般不宜超过( )。
A.3.0m B.5.0mC.6.0m D.10.0m
参考答案:C
Food safety issues, ____ will seriously affect the growth of teenagers and even the nation's future. [ ]
A. if not solved properly
B. not if solved properly
C. if solved properly
D. not if properly solved
城市污水处理厂,曝气沉砂池水平流速()m/s。
A.0.1
B.0.2
C.0.3
D.0.4