A straw has two holes. As proof, a thought experiment.
Imagine you have a sheet of paper. You cut a hole in it. You now obviously have one hole.
Now take another sheet of paper and cut a hole in that one as well. You now very obviously have two holes.
Now take a third sheet of paper. You join a point on one end to a holed sheet of paper and join a point on the opposite side to the other holed sheet of paper.
You continue joining points around the holes. Eventually the third sheet of paper becomes a tube. The original two holes are the ends of the tube.
The third sheet of paper could easily be rolled into a tube by itself, but this is to illustrate that each end of the tub is its own hole.
I forgot the straw!
A straw has two holes. As proof, a thought experiment.
Imagine you have a sheet of paper. You cut a hole in it. You now obviously have one hole.
Now take another sheet of paper and cut a hole in that one as well. You now very obviously have two holes.
Now take a third sheet of paper. You join a point on one end to a holed sheet of paper and join a point on the opposite side to the other holed sheet of paper.
You continue joining points around the holes. Eventually the third sheet of paper becomes a tube. The original two holes are the ends of the tube.
The third sheet of paper could easily be rolled into a tube by itself, but this is to illustrate that each end of the tub is its own hole.