脚手架按常用材料分为( )。

A．木脚手架、竹脚手架和金属脚手架
B．外脚手架和里脚手架
C．多立杆式脚手架和门形脚手架
D．悬吊式脚手架和挑式脚手架

The color display will use both chrominance and luminance information. A black and white display uses (74) .

A．neither of the two components

B．the chrominance component

C．the luminance component

D．both of the twocomponents