The audience was quite disappointed at the film because it wasn't such a good film( ) the advertisement had promised them. A. which B. as C. that D. like

步骤 1：理解句子结构
句子的主干是"The audience was quite disappointed at the film"，表示观众对电影感到失望。后半句"because it wasn't such a good film( ) the advertisement had promised them"是原因状语从句，解释了观众失望的原因。

步骤 2：分析从句结构
从句中"such a good film"是被比较的对象，"the advertisement had promised them"是广告所承诺的内容。这里需要一个连接词来连接"such a good film"和"the advertisement had promised them"，使得从句结构完整。

步骤 3：选择合适的连接词
选项A "which" 通常用于非限制性定语从句，不符合此处的语境。
选项B "as" 可以用于引导定语从句，表示"正如"，符合此处的语境。
选项C "that" 通常用于限制性定语从句，但此处需要一个连接词来表示"正如"，"that"不适用。
选项D "like" 通常用于比较，但此处需要一个连接词来引导从句，"like"不适用。