Does a straw have one hole 或者 2 holes?

Both

2 holes because there's two openings on either side of it. However that is because it is a cylinder object. A tube does not count as a singular hole. If something is a 圈, 圈子 ( a traditional one without dimensions) and it has a hole in it. Then it's hollow.

A straw is one very long hole
An elongated drinking hole, some call it

depends how hard 你 suck on it

Dunno 哈哈 but I have three