這句中文是甚麼？

主禮人在完結其致辭時表示感謝所有人仕一直以來所做的工作, 都是配合形成一個成功的會議。what=relative pronoun = thing/things that = all that 所有事情

1) I would like to close by thanking all those responsible for organizing whathas been a very successful conference.
兩句最明顯/重要的分別在於 巧用what has been 在時間及句子結構上的重大寓意:
has been :=致辭時 會議即仍未結束/仍在進行,大家仍可看到事前籌備到現在這刻所有會議程序=一直以來到現時這一刻所做的所有/一切事情更重要的文法及句子結構分析:a very successful conference 是what has been 的 objectcomplement , (modify 修飾 what hasbeen) 這表示不同人仕一直以來所籌辦的事情/工作, 都是配合形成一個成功的會議。 (任何一個籌備工作都是促成這個會議的成功因素)2)I would like toclose by thanking all those responsible for organizing a very successfulconference. 致辭時, 會議早己結束/告一段落 (organize a very successful conference 用 現在式表示已完結的程序 ) 沒有談及其他因素, 句子結構簡單

如果不用 what have been 可以改用 such.

I would like to close by thanking all those responsible for organizing what has been a very successful conference.

最後, 我想多謝那些令是次會議這樣成功的每一位(負責人)。

close by 應該是用作類似致詞演說的結尾
我的不是逐字譯, 而是照context譯, 希望幫到忙