for the purposes of the test the right answer is just a horizontal line relative to the ground, not sure they care if it looks like it's approximating the volume or not. so the errors they're talking about are not that. horizontal to the bottom of the bottle? something else? i'm having trouble wrapping my head around what alternate wrong answers there could be, my first instincts on it were that it seems too easy and there has to be a trick if there's a bunch of people failing it.
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