究 (w)

(jiū) after all; to investigate; to study carefully; Taiwan pr. [jiu4]

究其根源 (w)

(jiūqígēnyuán) to trace something to its source (idiom)

究竟 (w)

(jiūjìng) after all (when all is said and done); actually; outcome; result

究办 (w)

(jiūbàn) to investigate and deal with