Also, they're all tributaries of the Thames.
When I pointed this out on the night, someone responded "they're all full of water, too, but you wouldn't get the points for that."
Which only goes to prove my point: the setter of this question should have tried harder to make sure that the answer they were looking for was the only sensible one that answers the question.
To quote the Guidance for Question Setters: "Do not include questions with more than one, or indeed multiple, answers. Make sure each question you have written only has ONE correct answer."
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