The decreasing order of acidity is : `H_(2)O gtR-O-HgtH-C-=C-H.`
Explanation : `H-O-H ,RtoO-H,H-C-=C-H`
Alcohol is a weaker acid than water because alkyl group with +I effect (electron relasing effect ) makes the release of `H^(+)` ion more difficult. Ethyane is weaker acid than alcohol because `-=C-H` bond has less polarity as compared to O-H bond
