hisheadsoonappearedoutofoneofthesecondstoreywindows,__hecouldseenothingbuttrees.
a.fromwhichb.fromwherec.whered.fromthere
麻烦帮我分析一下句子结构..定语从句的话为什么选b不选a啊?先行词是thesecondstoreywindows吗?从句缺的是什么成分啊?