For accessibility assistance, which of the following programs is an on-screen keyboard?

A.
xkb

B.
atkb

C.
GOK

D.
xOSK

Explanation/Reference:
From the GOK homepage:
GOK is an on-screen keyboard that provides access to the GNOME desktop via dynamically generated keyboards, and text entry via one of the provided alphanumeric keyboards, or a dynamic keyboard created based on the users current system keyboard driver, or even a user made keyboard.

xOSK = seems to be nothing
atkb = seems to be nothing
xkb = In the X Window System, the X keyboard extension or XKB extends the ability to control the keyboard over what is offered by the X Window System core protocol.