多项选择题 What are the main factors that affect the feasibility of making any changes to existing document storage?( )A.social-acceptance ,training ,communication and teamworkB.technical-security,retrieval,access,control,liabilty and ownershipC.environmental-paper use , confidential waste, recyling , powerusageD.financial-capital costs , running costs ,contract terms , inflation

未知题型 气门传动组配气相位的变化规律是（）。

未知题型 起动机中磁极的作用是（）。