项目市场调查的方法主要有（） ["询问法","观察法","实验法","德尔菲法","指数平滑法"]
下列关于主体结构混凝土工程施工缝留置位置的说法，正确的有（）。 ["柱留置在基础、楼板结构的顶面","单向板留置在平行于板的长边位置","有主次梁的楼板，留置在主梁跨中1\/3范围内","墙留置在门洞口过梁跨中1\/3范围内","高度较大的柱、墙、梁以及厚度较大的基础可根据施工需要在其中部留设水平施工缝"]
Small businesses face unique customer challenges, which three challenges are small businesseslooking to overcome?（） [" technical staffing"," data center deployments"," employee training"," cost containment"," operational efficiency"," customer responsivene"]
森林群落有哪些基本特征？
在渗水量不大、稳定的黏土层中，深5m，直径2m，的圆形沉井宜采用（）。 ["水力机械排水下沉","人工挖土排水下沉","水力机械不排水下沉","人工挖土不排水下沉"]
电流互感器二次开路有何危害？
