Since Jonas Salk came up with his polio vaccine, infantile paralysis has virtually disappeared from the United States.

A．surfaced with

B．raised the price of

C．discovered

D．elevated

编制设备安装工程概算时，当初步设计的设备清单不完备，或仅有成套设备的重量时，可采用( )编制概算。

A．概算指标法

B．扩大单价法

C．预算单价法

D．设备费的百分率法