Comprehensive and Detailed In-Depth Explanation:
SC.L2-3.13.8 requires "implementing FIPS-validated cryptographic mechanisms to protect CUI confidentiality in transit." AES-256 is approved, but the module implementing it must be FIPS 140-2/3 validated (C), per CMMC. Open-source (A), usability (B), and complexity (D) aren't FIPS requirements.
Extract from Official CMMC Documentation:
* CMMC Assessment Guide Level 2 (v2.0), SC.L2-3.13.8: "Use FIPS 140-2/3 validated modules for CUI transit."
* NIST SP 800-171A, 3.13.8: "Verify FIPS validation of crypto modules." Resources:
* https://dodcio.defense.gov/Portals/0/Documents/CMMC/AG_Level2_MasterV2.
0_FINAL_202112016_508.pdf

The Assessment Plan (planning agreement) must be signed by both the Lead Assessor and the OSC Assessment Official. This formalizes agreement on scope, resources, and methodology. The C3PAO is responsible for overall oversight but does not co-sign the plan.
Exact extracts:
* "The Lead Assessor is responsible for developing the Assessment Plan in collaboration with the OSC Assessment Official."
* "Both the Lead Assessor and the OSC Assessment Official must sign the Assessment Plan to proceed."
* "The C3PAO maintains responsibility for quality assurance and submission, but not signing." Why other options are incorrect:
* A/B: Both signatures are required, not one alone.
* D: The C3PAO does not sign the planning agreement.
References:
CMMC Assessment Process (CAP), Assessment Planning.

MP.L2-3.8.4 requires that CUI markings follow the media, meaning when electronic documents are printed, the original markings must carry over to the hard copy. Distribution lists or colored stamps are not specifically required.
Extract:
"Mark media containing CUI with the CUI designation indicators as required. When converting CUI from one medium to another, the original markings must be retained." Thus, the assessor should expect to see the original markings carried onto the printouts.
Reference: CMMC Assessment Guide - Level 2, MP.L2-3.8.4.

Comprehensive and Detailed in Depth Explanation:
In a multi-cloud environment, assessing AC.L1-3.1.20 (external connection authorization) and AC.L2-3.1.13 (remote access confidentiality) is complex due to distributed resources and reliance on CSP controls. The CCA faces challenges in verifying how external connections are authorized (e.g., inconsistent methods across CSPs) and in obtaining sufficient evidence of cryptographic mechanisms (e.g., limited documentation of TLS or VPN use), as noted in the scenario. The volume of data further complicates tracking specific remote access activities, aligning with CAP guidance on evidence collection in hybrid environments.
Option A (outdated infrastructure) is unrelated to the described cloud context. Option B (physical security focus) is irrelevant to remote access controls. Option C (policy verification and personnel) is less specific than the scenario's focus on authorization and cryptography evidence. Option D precisely captures the challenges, making it the correct answer.
Reference Extract:
* CMMC Assessment Process (CAP) v1.0, Section 4.3:"Cloud environments may present challenges in verifying external controls and cryptographic evidence due to distributed architectures."
* NIST SP 800-171A, AC-3.1.20 & AC-3.1.13:"Assessors must verify authorization and cryptography across all external connections."Resources:https://cyberab.org/Portals/0/Documents/Process- Documents/CMMC-Assessment-Process-CAP-v1.0.pdf;https://csrc.nist.gov/pubs/sp/800/171/a/final

Comprehensive and Detailed in Depth Explanation:
The CAP mandates assessing all practices, making Option A correct. Options B, C, and D violate CAP and CoPC standards.
Extract from Official Document (CAP v1.0):
* Section 2.1 - Evidence Collection (pg. 24):"All practices must be assessed as required by the CMMC Assessment Process." References:
CMMC Assessment Process (CAP) v1.0, Section 2.1.