檐口第一根挂瓦条应保证瓦头出檐口（）mm。A.50~70 B.50~60 C.40~

承包人在施工中提出的涉及对设计图纸或施工组织设计的变更及对材料、设备的合理化建议，需经( )同意。

A．设计单位

B．施工单位负责人

C．发包人

D．监理工程师

系统调查

Diana bought a stereo for $530, which was the retail price plus a 6 percent sales tax. How much money could she have saved if she had bought the stereo at the same retail price in a neighboring state where she would have paid a sales tax of 5 percent ？（）

A．$1.00

B．$2.65

C．$4.30

D．$5.00

E．$5.30

RNA经NaOH水解，其产物是2’-核苷酸/3’-核苷酸和5’-核苷酸的混合物。( )

高炉要求上下渣比要（），有利于铁口维护。

A.高

B.低

C.相等