Could, may and might

Could, may and might are all used to express degreees of certainty.

1. Could suggests a less strong possibility than may or might.

2. Might is more tentative than may or could.

Which do you think is correct, #1 or #2?

Yeah, neither, same as Incho.

I could say "Might and could are more tentative than may, and might and could are exactly the same."
There's not much difference between them, though. People might say "may" when they mean "might", or "might" when they mean "may", so in the end they are all used to express the same concepts.

I don't like "may" much, I rarely use it, except for sentences like "Today is May fifth".

I don't know why they do it, but some of those basic grammars seem to draw the students' attention to all sorts of ways to expend energy needlessly nitpicking over inconsequential matters. 

CJ