单选题
The phrase “unable to comply” is used ( ) .
A
by the controller before he amends the clearance or instruction
B
by the pilot to advise the controller he cannot carry out the clearance or instruction received
C
by the pilot before he takes action on the clearance or instruction received
D
by the controller to inform that he cannot comply with the pilot’s requirement
答案解析
正确答案:B
