"—DKR, extend your downwind for _______ . —Roger, DKR."
A.delaying
B.spacing
C.sequencing
D.either B or C
正确答案是D
"—DKR, extend your downwind for _______ . —Roger, DKR."
A.delaying
B.spacing
C.sequencing
D.either B or C
正确答案是D