For the arriving A/C whose engines partially fail, the controller should _______ .
A.notify concerned emergency unit at the airport to be ready before the A/C lands
B.leave the altitude the A/C occupies and the altitude below the A/C unoccupied, prohibit the activities of other A/C and irrelevant vehicles in the maneuvering area
C.allow the A/C to proceed to the destination airport at favored altitude
D.A, B and C
正确答案是D