Tom is the only one of the workers who were praised at the meeting.对还是Tom

错。应为Tom is the only one of the workers who was praised at the meeting.意思是Tom是会议上唯一被表扬的员工。 the only one of 是“唯一一个”。
也可以是Tom is only one of the workers who were praised at the meeting.这是说Tom是会议上被表扬的员工中的一个。这里only是“仅仅、只是”，one of the workers是“员工中的一个”。
有the和没the差别很大。

Tom是在会议上收到表扬的唯一一名员工。

Tom是会议上唯一被表扬的员工

were应该改为was,the only one of 名词复数 +三单动词.
表示tom。翻译：tom是唯一的在会上受表扬的工人。

不知道你问什么，但是我认为你想让大家帮忙改正句子。所以希望对你有帮助哦