It was also partly motivated by an attempt to understand the extent to which antiretroviral treatment is reducing overall levels of mortality in South Africa.求大神分析这个句子,尤其是to which的作用,
网友回答
to some/the extent 某种程度,wich引导定语从句,先行词为extent,介词保留.
======以下答案可供参考======
供参考答案1:
which 可以省略，to起介词的作用。