The project will help people understand the many threats to the natural environment endangered plants and animals live.
A. which
B. when
C. where
D. that
网友回答
A. which
B. when
(答案→)C. where
D. that
解析：C 考查定语从句。句意：该项目将帮助人们理解濒危植物和动物生活的自然环境所面临的许多威胁。分析句子成分可知，空处引导定语从句，且在定语从句中作状语，先行词为the natural environment，故用where引导定语从句。