investigate at first hand的用法和樣例：
例句
- These direct investigations aim at addressing problems at a higher level by adopting a proactive and preventive approach.
進行直接調查的目的，在于以積極主動的態度，從較高層次著手解決問題。 - Reports of all direct investigations completed are available for public scrutiny at the office's Resource Centre.
已完成的直接調查報告均存放于公署的資源中心，歡迎市民索閱。
