Digital Signature:A digital signature is a mathematical scheme for verifying the authenticity of digital messages or documents.A digital signature provides message integrity, message authentication but not confidentiality.Non-repudiation deals with digital signatures which gives the assurance that someone cannot deny the validity of somethingTherefore a digital signature is required for non-repudiation of communication by a sender. Hence option 1 is correctImportant Point:Message authentication:It ensures that message has been sent by a genuine identity and not by an imposter. In this, the receiver needs to be sure of the senders identity. It is a service beyond message integrity.Message integrity:It means that data must arrive at the receiver exactly as they were sent. There must be no changes during the transmission, neither accidentally nor maliciously.Message confidentiality:It means that the sender and the receiver expect confidentiality. The transmitted message must make sense to only the intended receiver. To all others, the message must be garbage.