During testing, a team member escalates a quality defect to the project manager. While brainstorming with the team, the project manager realizes there is more than one cause of the problem. Which should the project manager use to identify the primary cause? 在测试期间，一位团队成员将某个质量缺陷升级上报给项目经理，在与团队进行头脑风暴时，项目经理得知问题的原因不止一个，项目经理应该使用哪一项来识别主要原因？ ◑A.Scatter diagram 散点图 ◑B.Statistical sampling 统计抽样 ◑C.Ishikawa diagram 石川图 ◑D.qualitative risk analysis 定性风险分析
