单选题
Your ______ effort is absolutely needed to find out what caused this accident.
A. cooperatively
B. cooperation
C. cooperative
D. cooperate
【正确答案】
C
【答案解析】初级问题 所有格和名词之间应填入形容词。所有选项都是从同一单词派生而来，按顺序分别是副词、名词、形容词和动词。
[高频词语] absolutely 绝对地 find out 发现，查明