And even though most of the decisions at what is effectively Asia's largest political pantomime are pre-determined, it's still worth having a think about some of the big economic priorities for China's leaders.

请问：

(1) decisions 后为什么用at？

【答】decisions 与at 无关。实际上，at 跟pantomime有关，pantomime 的意思是“哑剧，闹剧”，新闻英语中把pantomime 谐喻为“会议”。我们知道，介词at 常与meeting, conference, congress, discussion, lecture 之类的词语搭配，当然也可跟pantomime 搭配。what is effectively Asia's largest political pantomime 是一个名词从句，相当于一个名词，意为：亚洲最大的政治会议。

(2) at what is effectively Asia's largest political pantomime 是状语吗？

【答】at what is effectively Asia's largest political pantomime 意为“在这个实际为亚洲最大的政治会议上”。从本句的修饰关系看，应为定语，修饰most of the decisions。