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Iran remains an enigma for the outside world.

伊朗对外部世界而言依然是个谜。

《柯林斯英汉双解大词典》

The origin of these peculiar glassy spheres remains an enigma.

这些奇特的玻璃球体的起源仍然是个谜。

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and Linklater found the real Welles within those iconic characters "He is an enigma.

VOA: standard.2009.12.17

He is an enigma though who is his own man and does his own thing.

BBC: Steve Parrish's MotoGP column

Speaking outside Newcastle Crown Court, John Sampson, assistant chief constable of West Yorkshire Police, branded Bieber an enigma.

BBC: NEWS | UK | England | The hunt for a policeman's killer

Big institutional investors may sell because their policies forbid them to own stock in a company that has become an enigma.

FORBES: Correction Appended