The correct answer is C. A toll free telephone number.
A paging access number is a toll free telephone number that is used to page someone. When a person is paged, they receive a message on their pager that tells them to call a specific number. The paging access number is the number that they call to receive the message.
A toll free telephone number is a telephone number that is free to call from anywhere in the United States. These numbers are typically used by businesses and organizations to provide customer service or to make it easy for people to contact them.
An e-mail id is a unique identifier that is used to send and receive electronic mail. It is typically a combination of letters and numbers that is used to identify a specific user on an e-mail server.
A username is a unique identifier that is used to log in to a computer system or website. It is typically a combination of letters and numbers that is used to identify a specific user on a system.
A registration number is a unique identifier that is used to identify a specific product or service. It is typically a combination of letters and numbers that is used to track the product or service.