before and until

[joham]

This was one of China's 2005 university admission examination questions (for Shanddong Province):
It was some time ______ we realized the truth.
A. when B. until C. since D. before
The given answer was 'until', but I would think 'before' works as well. Am I right? My reason comes from:


Martin Hewings' ADVANCED GRAMMAR IN USE (2005 edition, Cambridge), unit 79:
We had to wait six weeks until/ before the parcel arrived.
It wasn't long before/until he was appointed Professor of Chemistry.

 

[Shakespeare's brother]

Both of these work ideally in the sentence you were given. 'Before' and 'until' have slightly different meanings, but overall their effect is identical.