The correct answer is "Elliptic curve discrete logarithm problem". Modular exponentiation in elliptic curves is the analog of the modular discreet logarithm problem.
* Answer "Prime factors of very large numbers" is incorrect because prime factors are involved with RSA public key systems; answer c is incorrect because modular addition in elliptic curves is the analog of modular multiplication; and answer "Knapsack problem" is incorrect because the knapsack problem is not an elliptic curve problem.

Data remanence is the biggest threat in the scenario where a flash drive has been overwritten and released to a third party for destruction. Data remanence is the residual or leftover data or information that remains on a storage media after it has been erased, deleted, or destroyed. Data remanence can pose a security risk, as it may allow the unauthorized access, recovery, or disclosure of the data or information by malicious or unintended parties, and compromise the confidentiality, integrity, or availability of the data or information.
Data remanence can be prevented or reduced by using various methods or techniques, such as overwriting, degaussing, or physical destruction, to ensure that the data or information is completely and irreversibly removed from the storage media. Data remanence is the biggest threat in the scenario where a flash drive has been overwritten and released to a third party for destruction, as it may still be possible for the third party to recover or retrieve the data or information from the flash drive, despite the overwriting and destruction processes. This is because flash drives use a type of storage media called flash memory, which is a non-volatile and rewritable memory that stores data or information in cells or blocks. Flash memory has a limited number of write cycles, which means that it can only be overwritten a certain number of times before it becomes unusable or unreliable. Flash memory also uses a technique called wear leveling, which distributes the write operations evenly across the cells or blocks, to extend the lifespan and performance of the flash memory. However, these characteristics of flash memory can also make it difficult to overwrite or erase the data or information completely and securely, as some cells or blocks may not be overwritten or erased due to the write cycle limit or the wear leveling technique, and may still

"SLE x annualized rate of occurrence (ARO) = ALE" pg 70 Shon Harris: All-in-One CISSP Certification

The advantages of SSO include having the ability to use stronger passwords, easier administration as far as changing or deleting the passwords, minimize the risks of orphan accounts, and requiring less time to access resources.
Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, 2001, John Wiley & Sons, Page 39