Question: D6 Fantasy is a role-playing game stand-alone rulebook published by what company?

Context paragraphs:
D6 Fantasy: D6 Fantasy is a generic fantasy role-playing game (RPG) based on the D6 System.  D6 Fantasy is published as a stand-alone rulebook (not dependent upon or requiring any other D6 System rulebook) and is supported by its own line of supplements.

The Complete Wizard's Handbook: The Complete Wizard's Handbook is a supplementary rulebook published in 1990 for the 2nd edition of the "Advanced Dungeons & Dragons" fantasy role-playing game.

D6 Space: D6 Space is a generic science fiction role-playing game (RPG) based on the "D6 System".  Although derived, in part, from material originally presented in "The Star Wars Roleplaying Game", "D6 Space" is published as a stand-alone rulebook (not dependent upon or requiring other D6 System or Star Wars rulebooks) and is supported by its own line of supplements.

The Castle Guide: The Castle Guide is a supplemental rulebook published in 1990 for the 2nd edition of the "Advanced Dungeons & Dragons" fantasy role-playing game.

The Complete Thief's Handbook: The Complete Thief's Handbook is a supplemental rulebook published in 1989 for the 2nd edition of the "Advanced Dungeons & Dragons" fantasy role-playing game.

The Complete Fighter's Handbook: The Complete Fighter's Handbook is a supplemental rulebook published in 1989 for the 2nd edition of the "Advanced Dungeons & Dragons" fantasy role-playing game.

D6 System: The D6 System is a role-playing game system published by West End Games (WEG) and licensees.  While the system is primarily intended for pen-and-paper role-playing games, variations of the system have also been used in live action role-playing games and miniature battle games.  The system is named after the 6-sided die, which is used in every roll required by the system.

Complete Psionic: Complete Psionic is a supplemental rulebook for the 3.5 edition of the "Dungeons & Dragons" role-playing game published by Wizards of the Coast and released in April 2006.  It is the first 3.5 edition supplemental rulebook published by Wizards of the Coast which focuses on psionics since the "Expanded Psionics Handbook".

D6 Adventure: D6 Adventure is a generic role-playing game system based on the D6 System.  "D6 Adventure" is published as a stand-alone rulebook (not dependent upon or requiring any other D6 System rulebooks) and is supported by its own line of supplements.

The Complete Priest's Handbook: The Complete Priest's Handbook is a supplemental rulebook published in 1990 for the 2nd edition of the "Advanced Dungeons & Dragons" fantasy role-playing game.

Supporting paragraphs: D6 Fantasy D6 System
Answer: West End Games