A checkbox is created in Expression Web by adding an Input (Checkbox) form ____ to the form element.

____________________ software provides users with a convenient means of creating documents containing complex mathematical calculations.

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

In a _____ system, the distinction blurs between input, output, and the interface itself.

A. user-centered B. topology-centered C. system-centered D. network-centered