A company wants to ensure that their company`s users are authenticated when they access resources defined in their Azure account. Which of the following is the correct definition of authentication?

Answer options:

A.This specifies the type of service you can use in Azure.
B.This specifies the type of data you can use in Azure.
C.This is the act of providing legitimate credentials.
D.This specifies what you can do in Azure.

Answer - C 
The definition of Authentication and Authorization is given in the Microsoft documentation. 

The other options are all incorrect because these are all user cases of Authorization. 
For more information on authentication, please visit the below URL- 

https://docs.microsoft.com/en-us/azure/active-directory/develop/authentication-scenarios