名词
中文翻译：Unknown
同义词：
['U-key', 'U-pass', 'U-token例句：1. The company issued a U-certificate to the new employee as proof of employment.（公司为新员工颁发了U证书，作为雇佣证明。）']
例句：
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1. The company issued a U-certificate to the new employee as proof of employment.
公司为新员工颁发了U证书，作为雇佣证明。
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2.The U-certificate is required for access to the restricted area.
进入受限区域需要出示U证书。
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3. The U-certificate was used to verify the authenticity of the documents.
使用U证书来验证文件的真实性。