say quite justifiably;say sth with certainty ❍ ～，确可信据。(《聊斋志异·段氏》)It is said with definite evidence,therefore it can be believed beyond all doubt. ❍ 她说的可能是真情，因为她～。What she said might be the actual state of affairs,for she said it with certainty.
言之凿凿yán zhī zuò zuò
凿凿：确实。说得十分确实可靠。speak on good grounds, say sth. with certainty