Charles Mott works for a company called VeriSign that acts a trusted third party to verify information. One of Charles' largest clients is CheckMd, which holds and authenticates customer reviews of doctors and dentists online and having a third party validating the reviews is critical to CheckMd's success. What type of authentication technique is VeriSign providing for CheckMD.

It is one of the type of electronic document that is used in the form of digital certificate process for the security purpose. It is also known as the certification authority.

According to the given question, Charles Mott is basically works for the VeriSign organization and for validating all the information provided by the third party they uses the certificate authority document technique for evaluating all the data.

Therefore, Certificate authority is the correct answer.