expression, godan verb (-tsu)
find someone's weak spot; hit a sore point
Idiomatic use: to pinpoint a hidden weakness or sensitive point in an argument or person. The literal meaning 'to drill a hole' is rarely used in modern Japanese; the phrase is almost always figurative.
彼の指摘はまさに穴を穿つものだった。
His remark really hit a sore point.
その
The question sharply exposed the opponent's contradiction.