Longitudinal separation minima based on time (aircraft flying at the same cruising level on the same track) shall be _______ .a. 15 minutes; b. 10 minutes, if navigation aids. Permit frequent determination of position and speed;c. 5 minutes between aircra
A.a, c and d
B.a and b
C.a, b and c
D.All above
正确答案是D