Please explain why each statement is either true or false :)

Which of the following statements about cryptography are true? Public-key encryption is more efficient than shared key encryption, in the sense that information can be encrypted and decrypted faster. Using public-key cryptography, it is possible to check that the informationen really comes from the claimed sender. With symmetric encryption, both the sender and the receiver need to know the secret key. With shared key cryptography, the shared key can be published freely. A weakness with public-key encryption is that the public key can only be used once