在RVSM空域紧急情况下须绕飞，又无法联系到ATC，下列哪项动作不必要？ Which of the following act

在RVSM空域紧急情况下须绕飞，又无法联系到ATC，下列哪项动作不必要？ Which of the following actions is not needed when the emergency situation that the flight crew should fly around without connecting ATC happens in RVSM airspace?

A.在旅客广播系统中做机长广播， 通告乘务员及旅客当前飞机情况 Using PA system to give captain broadcast,notify the current situation to flight attandants and passengers

B.在121.5及123.45频率上广播自己的位置、高度、意图 Broadcasting position, flight level and intention on 121.5 and 123.45MHz

C.打开全部外部灯光 Illuminating all exterior lights

D.保持TCAS工作，保持目视观察 Keep TCAS work normally and maintain visual observation

正确答案是A