Q. If I want to save a plot to a PDF file, which of the following is a correct way of doing that?

• (A) Construct the plot on the screen device and then copy it to a PDF file with dev.copy2pdf()
• (B) Construct the plot on the PNG device with png(), then copy it to a PDF with dev.copy2pdf()
• (C) Open the PostScript device with postscript(), construct the plot, then close the device with dev.off()
• (D) Open the screen device with quartz(), construct the plot, and then close the device with dev.off()