Which of the following statements about VOR is TRUE according to the text?
A. VOR signals are more easily affected by terrain feartures and coastlines.
B. VOR signals can nottravel beyond the horizon.
C. VOR signals are only useful in perfectly clear days.
D. VOR signals are limited by the sight of the pilots .
查看答案
What is the advantage of VOR navigation compared with NDB navigation?
A. larger coverage
B. less maintenance
C. greater accuracy
D. higher service altitude
Which of the following is NOT a disadvantage of VOR navigation?
A. limited range
B. significant cost
C. closer to mountains
D. vulnerable to diffraction
扦插难生根树种最好用( )。
A. 硬枝扦插
B. 嫩枝扦插
C. A+B
扦插难生根树种,在枝龄相同的条件下,应采( )。
A. 树干基部萌芽枝
B. 树干(或苗干)上的一级侧枝
C. 树干上部的枝条
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