Question 7
Why does the liquid travel up the straw when you drink through one?
The right answer is the one marked above.
The outside atmospheric pressure pushes the liquid into the straw. Sucking lowers the pressure inside the straw, while at the liquid surface outside it the pressure is still atmospheric.
All we do is lower the pressure inside — the pushing is done by the atmosphere, not by us. Raising the pressure inside the straw would drive the liquid the other way, downwards.