Spudgunjon,
Good spot, I have been back into the AMM and the engine shutoff valves are 28V DC BAT BUS powered, not HBB as my quiz states.
For info, I first posted those quizzes up almost 10 years ago and nobody else has spotted that yet. I occasionally get queries about the quiz answers but they all seem to be correct after the inevitable initial errors which were ironed out early on. This leads me nicely onto Rainboes point that any website, book or other source may have errors and you should always go by your company FCOMs. That said even Boeing material has errors!
Finally, note that my quizzes are for Classics. At the foot of the quiz page is a section on NG differences which could be significant in a fuel valve question.
S&L