同步发电机参数Xd″称为（）。
A.横轴暂态电抗
B.横轴次暂态电抗
C.纵轴暂态电抗
D.纵轴次暂态电抗
参考答案：D
网状模型的数据结构以( )为基础。
A．网结构
B．表结构
C．树结构
D．无向图
—He was a real sportsman, ________ he is not very well known.
—________. Besides, he was young. [ ]
A. though; I am afraid not
B. since; You are sure
C. even if; I agree absolutely
D. because; That's that point
