我們對這一事件作了周密的調查英文怎麼說？

We made a strict inquiry into the incident.

他開始調查火災的原因,接著調查了三個星期英文怎麼說？

He started an inquiry into the causes of the fire, and prosecuted it for three weeks.

他們對這一事件展開調查英文怎麼說？

They held an inquiry into the incident.

官方調查的目的是想得到那次事件的真相英文怎麼說？

The purpose of the official inquiry was to come at the true facts of the event.