所用电流互感器和电压互感器的二次绕组应有永久性的、可靠的保护接地。
参考答案：对
—John seems happy, even though his wife left him and he lost his job.
—I think he ________ to put on a brave face.[ ]
A. will try
B. has tried
C. tries
D. is trying
下列哪种图像格式的文件可以通过Acrobat5.0C“打开”命令直接转换为PDF文件？（）
A.DCS
B.GIF
C.PSD
D.RAW
