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In the node tree shown in the accompanying figure, "portfolio" is a _____ node of "author."

To pause, restart, or cancel a print job, open the print ____________________, click the name of the print job, then choose the desired option from the Document menu.

Fill in the blank(s) with the appropriate word(s).

__________ is needed to represent nothing in a given position.

a. Nothing b. A space character c. The digit zero (0) d. The base