Which of the Following Statements Is/are True Regarding a Digital

Which of the following statements is/are true regarding a digital signature?

A) It is generated from the contents of the message and the sender's private key.
B) Extra data are appended to an electronic message to identify and authenticate the sender and message data using public-key encryption.
C) If the receiver of a message sees that a digital signature is attached, the receiver can be confident that no one has altered the message and that the sender is who the sender claims to be.
D) It is generated from the contents of the message and the sender's private key and extra data are appended to an electronic message to identify and authenticate the sender and message data using public-key encryption.