Correct Answer - A
Acidic strength depends upon the tendency of a `molecule_(+)` to give a proton. Amond the given `CH_(3)CH_(2)OH_(2)` readily gives a proton so it is highly acidic `CH_(3)CH_(2)CH_(3)` has the least tendency to lose a proton, so its acidic strength is least among the given. thus the correct order of acidic strength is
`IV lt II lt I lt III`