tu vs vous

Question

The question required the use of "you" but did specify which you.  The correct answer was given as " que vous ne soyez"  I wrote " Que tu ne sois" and was marked wrong.  Not clear why?

Accepted Answer

Hi Kay,
The only Kwiz in that lesson with 'soyez' was:
Je vais vous ramener chez vous avant que vous ne soyez fatigués 
for 
I am going to bring  you home before you are too tired
So the context is there, you are talking about someone you say the polite 'vous' to or to a collection of people. The 'tu' form would be incorrect in that sentence.
Bonne Continuation !

Answer

Both are grammatically correct of course, so depends on whether there was a “contextual” indicator of formality or plurality. Do you remember the full sentence/question ? May be best reported through quiz report button, as easier to have this checked from there.