Should you write "some of the UK's longest tunnels..." or "some of the UKs longest tunnels..."?
closed as not a real question by Matt E. Эллен♦, Robusto, aedia λ, RegDwigнt♦ Mar 9 '12 at 17:29
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When an initialism is made possessive, it is treated as any other word. Also, never change the capitalization of an initialism. UK's is correct:
some of the UK's longest tunnels