（） are mounted in pairs to protect the boiler against overpressure. ["Safety valves","Water tubes","Steam stop valves","Blow down valve"]
下述（）是硅砖烘炉过程中的晶形转化点。 ["105℃","163℃","573℃","375℃"]
Chafing gear（）. ["reduces and prevents corrosion of standing rigging","prevents corrosion of running rigging","reduces and prevents wear caused by the rubbing of one object against another","protects the body against extreme cold"]
下列有关赤霉素生理作用的描述中，正确的是（）。 ["促使长日照植物开花","使未经春化作用的植物开花","解除种子的休眠，促使种子萌发","促使短日照植物开花"]
域名和地址通过（）服务器转换。 ["E-mail","WWW","DNS","FTP"]
何谓自给偏压电路？它有何特点？
