单项选择题
A.top or upstream beginning of a bend B.bottom or downstream beginning of a bend C.midpoint or center radius of a bend D.center line or apex of a bend
A.This is the best place to land B.You are seen - assistance will be given as soon as possible C.Tail block is made fast D.Slack away
A.the code flags FR B.a black ball over a black diamond shape C.code flag Quebec over a black ball D.two black diamond shapes in a vertical line