英语难句剖析（含较复杂的主语从句问题）

Which is exactly what organizers of the just wrapped Australia from above contest were likely aiming for when they launched the competition in March.

划线部分是什么样的句法成分？感谢老师回答。

Which is exactly what organizers of the just wrapped Australia from above contest were likely aiming for when they launched the competition in March.

整个句子其实是个定语从句，修饰前一句的某个词或词组或整个句子。which是关系代词，在从句中主语。is是系词，exactly为状语，what至句末是表语从句。what等于the thing which,在表语从句中作were aiming for的宾语。organizers of the just wrapped Australia from above contest为表语从句的主语，when they launched the competition in March.为表语从句的时间状语。