题目内容：
4. No one has yet succeeded in explaining the _________ of how life began.
(A) problem
(B) cause
(C) puzzle
(D) logic
参考答案：
选择题：4.No one has yet succeeded in explaining the _____
- 题目分类：西安理工大学-机械设计制造及其自动化-大学英语二2
- 题目类型：选择题
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No one has yet succeeded in explaining the _________ of how life began.
(A) problem
(B) cause
(C) puzzle
(D) logic