The number of people in these comments who already understand the self-siphoning nature of water with zero explanation required makes me so proud to be here among them.

Ha. Trick question! All of them are already full of air, and niether the flow rate nor the direction (or lack) of gravity was specified anyway. You lose. :)

Depends on the flow rate, but most likely 1 if the tap is running fast. Otherwise I have no idea.

Also, what's with these comments? What's so special/clever about this pic?

I think, Number 7 will stay empty for some time.

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