Because verifying identity in the online world is difficult, certificate authorities take over that challenge.

由于在在线领域中证明某个实体的身份非常困难，认证权威就接管了这个挑战。

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Public transport is seen as the main solution, however the authorities are also aware that this will pose a major challenge.

公共交通体系是解决未来交通问题的一个很好的选择，然而，权威机构也意识到其所面临的巨大考验。

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This is a massive challenge for the authorities here in China to deal with .

这对中国的安全机关提出了巨大挑战。

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The author is careful not to directly challenge the authorities' version of what happened on Sept. 30.

CNN: RELIVING THE DAYS OF THE COUP

As Russians become better off, they are getting keener to challenge the authorities whether it is over Chechnya, pollution or education standards.

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Officials and activists say the biggest challenge for the authorities and society is to ensure that children are encouraged to report abuse.

BBC: NEWS | South Asia | Abuse of Indian children 'common'