Answer:
D. The Remote Authentication Dial-In User Service server certificate has expired.
Step-by-step explanation:
In the case when the employees report that the internet is not connected to the network also the technician verifies that there is no configuration changes made for the same so the most likely cause would be that the remote authentication i.e. the certificate of the dial in user server would have been expired
Therefore as per the given scenario, the last option is right