起搏冲动发生的细胞是：
A．结细胞
B．移行细胞
C．蒲肯野纤维
D．神经细胞
E．心肌细胞
参考答案：A
方程x（x-3）+2（x-3）=x2-8的解为（ ）
A．x=2
B．x=-2
C．x=4
D．x=-4
Under the International Code of Signals how are geographical locations such as New York City transmitted?（）
A.A commonly used abbreviation such as NYC is used
B.The name is spelled out
C.The geographical coordinates are used
D.The radio station call sign for the nearest marine radio station is used
