赞同曹老师解答观点

You mean it's become an issue that is continually being debated but left unresolved.

备注：that is continually being debated but (主语+is省略)left unresolved为关系代词that代替前面先行词“an issue” 引导限制性定语从句，关系代词在定语从句作主语成分。

【1】主动结构:主语+leave+宾语+宾补(过去分词充当)（备注：宾补可以是，形容词，副词，介词短语，现在分词，过去分词）

  He left such an important matter unfinished. 他让这样一件重要的事半途而废了。

【2】被动结构:主语+be+left+主补(过去分词充当)

Such an important matter was left unfinished by him.这样一件重要的事被他半途而废了。

【1】主动结构：主语+leave+宾语+宾补(形容词充当)

They left the window of the room open.他们让房间的窗户开着。

His illness left him weak.他的疾病让他身体很虚弱。

【2】被动结构：主语+be+left+主补(形容词充当)

The window of the room was left open by them他们让房间的窗户开着。

He was left weak by his illness .他的疾病让他身体很虚弱。