69. 下列何種心臟病史在進行牙科治療的風險評估時被評為最低風險？ (A) Recent myocardial infarction history (within the past 7 to 30 days) (B) Unstable angina (C) Stable [mild] angina and past history of myocardial infarction (D) Past history of ischemic heart disease with no other clinical risk factors