当电磁波的电场矢量的轨迹为一直线时，称这种电磁波的极化为（）.
A.线极化
B.水平极化
C.垂直极化
D.单极化
参考答案：A
期货公司被有权机关立案调查或者采取强制措施的，期货公司应当在（）个工作日内向其住所地的中国证监会派出机构书面报告。
A.3
B.5
C.10
D.30
As is known to all, the term "Lei Feng" _____ anyone who is selfless, or anyone who is ready to help
others in China. ?[ ]
A. focuses on
B. stands for
C. results from
D. turns to
