They are talking about which film they are going to see.(保持原句不变） They are taliking about___fiim __see.
问题描述：
They are talking about which film they are going to see.(保持原句不变）
They are taliking about___fiim __see.
答
They are taliking about which fiim to see.
用todo形式，是一种省略，注意到从句的主语仍是句子的主语，可省。
答
They are taliking about_which__fiim _to_see.
改成不定式短语