You have a full-color RGB document and you need to create a grayscale version that will print only on the black plate. How can you accomplish this?

Select everything in the document and then apply the Convert to Grayscale command.
Apply the Convert to Grayscale command and change the Document Color Mode to CMYK.
Use the Recolor Artwork command and select the 1-Color Job preset.
Delete all the color swatches from the Swatches panel except for Black and White.