answer all please

16. Select a correct statement regarding encryption methods B. Symmetric-key encryption method is used to authenticate trading partner Most companies profer using asymmetric hay eneryption method for data transmission C. Only asymmetric key encryption method can ensure confidentiality D. Asymmetric key encryption method is used to create digital signatures 17. Select a correct statement regarding digital signature? A digital signature is a message digost encrypted using the document creator's public key B. Either hashing or encryption, not both, is used to create a digital signature A digital signature can ensure data integrity and also authenticates the document creator D. To ensure data integrity, receiver's hashing algorithm should be different from sender's hashing algorithm 18. To ensure the data sent over the Internet are protected, which of the following keys is required to encrypt the data (before transmission) using an asymmetric-key encryption method? A Receiver's public key 8) Receiver's private key c. Sender's public key D. Sender's private key 19. Disaster recovery plan is a A Preventive control B. Detective control C. Application control D. Corrective control 20. One control objective for an operating system is that it must protect users from each other. Which of the following statements best explains this concept? A. User applications must not be allowed to gain control of or damage the operating system B. The operating system must be able to prevent unauthorized users from accessing, corrupting, or destroying other users' data No operating system module should be allowed to corrupt or destroy another operating system module. D. The operating system should be able to gracefully terminate activities, and later recover to its previous state 21. An auditor should be concerned about which of the following when reviewing the risks of a company's wireless network: A. Confidentiality B. Integrity C. Availability D. All of the choices are correct