If Bernhard Riemann says one, Imma say one. Plus Poincaré didn't disagree. They're undoubtedly two of the greatest mathematicians to ever live. One.
If a straw only had one opening, how many holes would it have? so if it has two openings, how many does it have? Come to think of it, if a straw had only one opening, would it still be a straw?
The oldest drinking straw in existence, found in a Sumerian tomb dated 3,000 BCE, was a gold tube inlaid with the precious blue stone lapis, and was used to drink beer. Boss.
Two is indefensible. I'm leaning toward zero. Holes perforate a surface. But that isn't at all the point with a straw. It's more like a slide that has been enclosed to control air pressure. You wouldn't say a slide has a hole.
A straw is a tunnel through which a beverage or saliva can flow. A tunnel is a type of hole. A hole is simply a gap in space.
Two. Definition of hole (Entry 1 of 2) 1a: an opening through something : PERFORATION The coat has a hole in it. a bullet hole Bullets can have entry and exit wounds--two holes. Seal one end of a straw and it's left with one hole.
In a related subject why do we call the little round fried dough things made from leftover dough “donut holes”?
