蛛网膜下腔出血最常见的病因是（）
A．抗凝治疗的并发症
B．脑动脉炎
C．高血压动脉硬化
D．脑血管畸形
E．先天性动脉瘤破裂
参考答案：E
— Do you know this city?
— No, this is the first time that I ______ here.[ ]
A. was
B. am
C. have been
D. had been
四轴如何向前、后、左、右、走？
