понятное дело

Etymology
lit. '(it's an) understandable affair/matter'.

Adverb

 * 1) obviously, of course, understandably, clearly, needless to say, unsurprisingly

Predicative

 * 1) it's obvious (that), of course, it's understandable (that), it's clear (that), it goes without saying (that), it's unsurprising (that)