中 * * 党从南昌起义、秋收起义中得到的最主要的教训是[ ]

A、必须保证党对军队的领导权

B、必须建立革命统一战线

C、必须将工作重心从城市转移到农村

D、必须武装反抗国民党反动派

A distress signal（）.

A.consists of 5 or more short blasts of the fog signal apparatus

B.consists of the raising and lowering of a large white flag

C.may be used individually or in conjunction with other distress signals

D.is used to indicate doubt about another vessel's intentions