On Tue, 23 Oct 2007 16:59:45 -0400, "HDRDTD" wrote:

Again, this one is debatable as both 'Suction' and 'Atmospheric Pressue' are
valid answers.

I think this one's reasonable - it's multi-choice, you do know that it's
one of the answers, and _only_ one of the answers. With that extra
axiom, the answer is clearly "atmospheric pressure" rather than
"cylinder suction".

Given what I learned from the balloons question, I think it's actually
local variations in non-constant air pressure between cylinders...

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