第28题: [单项选择]关于窦房结支的起源的描述,正确的是 A. 约40%起源于回旋支,60%起源于前降支 B. 约40%起源于回旋支,60%起源于右冠状动脉 C. 约40%起源于前降支,60%起源于右冠状动脉 D. 约40%起源于前降支,60%起源于回旋支 E. 约40%起源于右冠状动脉,60%起源于回旋支 参考答案:B
第31题: [单项选择]Cargo vessels being navigated,and fitted with emergency lighting and power systems,shall have their emergency systems tested at least once(). A. a month B. in each week C. in every 6 months D. in every 12 months 参考答案:B