硫酸盐还原菌测定中如果空白出现阳性反应，表明测定过程中无污染，本次测定有效。
参考答案：错
The newspaper says that all construction work ________ by 2012. [ ]
A. has been completed
B. has completed
C. will have been completed
D. will have completed
关于泡沫喷淋管道支、吊架安装间距说法正确的是（）。
A、与泡沫喷头之间的距离不应小于0.3mm
B、与泡沫喷头之间的距离不应小于0.8mm
C、与末端泡沫喷头之间的距离不宜大于0.5mm
D、与末端泡沫喷头之间的距离不宜大于1.0mm
