The Visual Approach Slope Indicator System, better known as VASIS, is a beam of light having a _______ color in its upper part and a _______ color in its lower part.
A.red……white
B.blue……red
C.while……red
D.green……red
正确答案是C
The Visual Approach Slope Indicator System, better known as VASIS, is a beam of light having a _______ color in its upper part and a _______ color in its lower part.
A.red……white
B.blue……red
C.while……red
D.green……red
正确答案是C