盘根究底

Explanation: Cross-examination, held the root causes of things. 　　Usage: Joint type; as predicate, object; refers to cross-examine, investigate the root causes of things 　　Source: Guo, "Can Chun and other words of three sad sheep": "I regret I should not have lost get to the bottom of things, so to suffer him." 　　Examples: I regret I should not be lost ~, so to suffer her. (Guo, "Shepherd sorrow words") Thesaurus:  run to ground, dig Make a thorough investigation of basio-, an inquiring (turn of) mind, Sougentichi, Digging to find the source of the, Pursuit ray tracing