As is the custom, police forensic experts carried out a painstaking search of the debris.

　　像往常一樣，警方的.法醫(yī)專家對殘骸進行了仔細的查看。

　　The mastery of a language requires/ needs painstaking effort.

　　要學好一種語言，必須下苦工夫。

　　I don't know how to make polite conversation.

　　我不曉得怎么說應酬話。

　　He had always been polite ─ she couldn't fault him on that.

　　他總是彬彬有禮——她在這方面對他無可指摘。