Have to say I totally agree with cc2180 on this one. I'd tick the 10k answer if in an exam. FM 18:- 9999.
What would I know, it's nearly always less than 10k over the North Sea.
Not entirely sure you would have a good case, in the event of getting it wrong, that you could argue the TAF was incorrectly written and not what you would expect to find in everyday use, with the missing letters here and there. Correct terminology.????
If in doubt, mark 'C'