问题补充：
We cannot figure out quite a number of insects, birds, and animals are dying out.
A. that
B. as
C. why
D. When
答案：
A. that
B. as
(答案→)C. why
D. When
解析：主要测试宾语从句。分析句子结构可知：动词短语figure out缺少宾语从句，同时后面句子中缺少状语，再结合答案可知能做状语引导宾语从句的词只有C和D，但是when又不符合语境。句子意思：我不能理解为何许多昆虫、鸟儿和动物濒临灭绝。例如：The teacher didn figure out why the youngest boy in the class was always being late for school。老师不理解为何年龄最小的男孩上学总是迟到。
