Phrase for asking the obvious
Solution 1:
You're looking for rhetorical affirmations.
In addition to the examples given in other answers,
Examples:
- Is the sky blue?
- Is the ocean salty?
- Is the sun hot?
- Is the atomic weight of Cobalt 58.9? (from Egon Spengler in Ghostbusters II)
Solution 2:
The g-rated version of 'does a bear sh*t in the woods?' is,
Is the Pope Catholic?