English translation for "a closed book"

谜, 未揭开的秘密 高深莫测的事物
指我们不懂的地方，例如

Example Sentences:

	1.	The man's early life is a closed book . 那人的早年生活是个不可告人的谜。
	2.	Nuclear physics is a closed book to most of us . 我们大多数人对原子核物理学一窍不通。
	3.	For me , geology is a closed book 对我来说地质学是一门我完全不懂的学科。
	4.	Nuclear physics is a closed book to me 核物理学是我完全不懂的一门学科。
	5.	A closed book 未揭开的秘密

Similar Words：

, "a close shave" English translation, "a close thing" English translation, "a close translation" English translation, "a close(narrow) shave" English translation, "a closed membership" English translation, "a closed scholarship" English translation, "a closed society economy" English translation, "a closed wages system" English translation, "a closed-door policy" English translation