如要调查消费者对茶叶产品的态度,应采用()市场调查法 ["A、询问法","B、观察法","C、试销","D、资料分析法"]
金属材料的机械性能指标有哪些?
石化装置的仪表伴热方式有蒸汽伴热和()伴热两种。 ["A、热水","B、热空点","C、电","D、油"]
顾渚紫笋主销() ["A、港、澳、东南亚地区和国家","B、外销日本","C、京、沪","D、京、津、穗"]
()管道用水作介质进行强度和严密性试验。 ["A、热力","B、煤气","C、天然气","D、工作压力低于0.07MPa"]
什么叫联接?联接怎么分类?