File services share data files and subdirectories on file servers.
Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the
Ten Domains of Computer Security, 2001, John Wiley & Sons, Page 99.

Threat modeling is a technique that evaluates the secure Bet principles of network or software architectures.
Secure Bet is an acronym that stands for security by design, security by default, and security by evaluation.
Threat modeling is a process that identifies and analyzes the potential threats and vulnerabilities that may affect the network or software architecture, and determines the appropriate countermeasures and controls to mitigate them. Threat modeling can help to design and implement a network or software architecture that is secure, resilient, and compliant with the security requirements and standards. The other options are not techniques that evaluate the secure Bet principles of network or software architectures, as they either do not focus on the threats and vulnerabilities, do not involve design and evaluation, or do not relate to security.
References: CISSP - Certified Information Systems Security Professional, Domain 8. Software Development Security, 8.1 Understand and integrate security in the Software Development Life Cycle (SDLC), 8.1.1 Identify and apply security controls in development environments, 8.1.1.1 Secure Bet; CISSP Exam Outline, Domain 8. Software Development Security, 8.1 Understand and integrate security in the Software Development Life Cycle (SDLC), 8.1.1 Identify and apply security controls in development environments,
8.1.1.1 Secure Bet

In computer science, hierarchical protection domains, often called protection rings,
are a mechanism to protect data and functionality from faults (fault tolerance) and malicious
behavior (computer security). This approach is diametrically opposite to that of capability-based
security.
Computer operating systems provide different levels of access to resources. A protection ring is
one of two or more hierarchical levels or layers of privilege within the architecture of a computer
system. This is generally hardware-enforced by some CPU architectures that provide different
CPU modes at the hardware or microcode level. Rings are arranged in a hierarchy from most
privileged (most trusted, usually numbered zero) to least privileged (least trusted, usually with the
highest ring number). On most operating systems, Ring 0 is the level with the most privileges and
interacts most directly with the physical hardware such as the CPU and memory.
Special gates between rings are provided to allow an outer ring to access an inner ring's
resources in a predefined manner, as opposed to allowing arbitrary usage. Correctly gating access
between rings can improve security by preventing programs from one ring or privilege level from
misusing resources intended for programs in another. For example, spyware running as a user
program in Ring 3 should be prevented from turning on a web camera without informing the user,
since hardware access should be a Ring 1 function reserved for device drivers. Programs such as
web browsers running in higher numbered rings must request access to the network, a resource
restricted to a lower numbered ring.
Ring Architecture
All of the other answers are incorrect because they are detractors.
References:
OIG CBK Security Architecture and Models (page 311)
and
https://en.wikipedia.org/wiki/Ring_%28computer_security%29

RFC 2828 (Internet Security Glossary) defines Key recovery as a process for
learning the value of a cryptographic key that was previously used to perform some cryptographic
operation.
Key encapsulation is one class of key recovery techniques and is defined as a key recovery
technique for storing knowledge of a cryptographic key by encrypting it with another key and
ensuring that that only certain third parties called "recovery agents" can perform the decryption
operation to retrieve the stored key. Key encapsulation typically allows direct retrieval of the secret
key used to provide data confidentiality.
The other class of key recovery technique is Key escrow, defined as a technique for storing
knowledge of a cryptographic key or parts thereof in the custody of one or more third parties called
"escrow agents", so that the key can be recovered and used in specified circumstances.
Fair public-key cryptography is a key splitting method proposed by Silvio Micali in which the pieces
of a private key can be individually verified by the Key Escrow Agencies to be correct, without
having to reconstruct the key.
Zero-knowledge is used in a zero-knowledge proof, where a prover convinces a verifier of a
statement (with high probability) without revealing any information about how to go about proving
that statement.
Source: SHIREY, Robert W., RFC2828: Internet Security Glossary, may 2000.