Well spotted, geevo. emmie was right behind, in second place.
With three possibilities for 'gnu', it's a question of eliminating the 'bad' locations. As far as 21,11,2 is concerned, 2 cannot be U as it is a singleton and couldn't have a Q in front the way the grid is constructed. As for 23,13,21, there are too many 23s for it to be likely to be G.
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