According to the BSA/AML Manual1, a financial institution is required to file a SAR for any transaction conducted or attempted by, at, or through the institution that involves or aggregates at least $5,000 in funds or other assets, and the institution knows, suspects, or has reason to suspect that the transaction (or a pattern of transactions of which the transaction is a part): (a) involves funds derived from illegal activity or is intended or conducted in order to hide or disguise funds or assets derived from illegal activity; (b) is designed to evade any requirements of the BSA or its implementing regulations; © has no business or apparent lawful purpose or is not the sort in which the particular customer would normally be expected to engage, and the institution knows of no reasonable explanation for the transaction after examining the available facts, including the background and possible purpose of the transaction; or (d) involves use of the institution to facilitate criminal activity. In this case, Bank A is the institution that processes the wire transfer and deems it suspicious, based on its own assessment of the transaction and the customer. Therefore, Bank A is responsible for filing a SAR for the transaction in Country A, where it is located and where the transaction takes place. Bank A does not need to file a SAR for the transaction in Country B or Country C, as it does not have jurisdiction or authority over those countries or the other banks involved. However, Bank A may share information about the suspicious transaction with Bank B or Bank C, subject to certain conditions and limitations, as described in the BSA/AML Manual1.
Reference:
BSA/AML Manual1
Suspicious Activity Reporting - Overview2
Suspicious Activity Report (SAR) Basics3
From Microsoft Start Partners
Another simpler way of looking at the problem is by seeing this case as a Correspondent Banking relationship:
-A is the primary correspondent bank.
-B is the respondent bank.
-C is the receiving bank (of the wire transfer).
Since A is conducting the transaction on behalf of B's customer via the correspondent relationship deemed suspicious, it is the transaction in Country A by the correspondent bank that files the STR. Also, per the regular process, it is on the transaction, not the bank, that the STR is filed against.

The Basel Committee's AML guidelines emphasize risk-based customer due diligence (CDD) and beneficial ownership transparency.
Option A (Correct): CDD policies must be risk-based to apply enhanced due diligence (EDD) for high-risk customers and simplified due diligence (SDD) for low-risk customers.
Option C (Correct): Banks must verify the identity of customers and beneficial owners to prevent financial crime risks.
Why Other Options Are Incorrect:
Option B (Incorrect): Numbered accounts are not strictly prohibited but require strict transparency and due diligence measures.
Option D (Incorrect): CDD procedures must be risk-based, not uniform across all customers.
Option E (Incorrect): Transactions should not be processed until full due diligence is completed, except in rare cases where regulatory exceptions apply.
Best Practices for Risk-Based Customer Due Diligence:
Apply EDD for high-risk entities (e.g., PEPs, offshore companies).
Ensure full beneficial ownership transparency.
Implement ongoing transaction monitoring for risk assessment.
Reference:
Basel Committee's "Sound Management of ML/TF Risks"
FATF Recommendation 10 (Customer Due Diligence)
6th EU AML Directive (6AMLD) on Beneficial Ownership Transparency

According to the Anti-Money Laundering Specialist (the 6th edition) study guide, when a financial institution receives a law enforcement inquiry, it should cooperate as much as possible and respond to all formal requests for information, unless there is a valid objection that can and should be made1. The institution should also file a suspicious transaction report (STR) if the inquiry or the customer's activity triggers any red flags or indicators of money laundering or other financial crimes2. Additionally, the institution should monitor the account for suspicious activity and review the money laundering risk posed by the account, as these are part of the ongoing due diligence and risk assessment processes3. Closing the account immediately is not a recommended action, as it may alert the customer or interfere with the investigation4.
Reference:
1: ACAMS, CAMS Certification Package - 6th Edition, Chapter 4, page 121
2: ACAMS, CAMS Certification Package - 6th Edition, Chapter 4, page 122
3: ACAMS, CAMS Certification Package - 6th Edition, Chapter 4, page 123
4: ACAMS, CAMS Certification Package - 6th Edition, Chapter 4, page 124

The compliance officer should recommend an audit for cash transactions since the last compliance review, as this would help to identify the extent of the problem, the root causes, and the potential risks involved. The audit would also provide evidence for corrective actions and remedial measures to prevent future occurrences of non-compliance. The compliance officer should not recommend terminating or suspending the teller's employment, as this would be premature and disproportionate without a thorough investigation and due process. The compliance officer should not recommend formally reprimanding the branch manager, as this would not address the underlying issues and could create a hostile work environment.
Reference:
ACAMS CAMS Certification Study Guide, 6th Edition, Chapter 5, page 1251 ACAMS CAMS Certification Video Training Course, Module 5, Lesson 12 ACAMS CAMS Certification Exam Outline, Domain 5, Task 33

According to the CAMS Study Guide, EDD is a higher level of scrutiny applied to customers who pose a greater risk of money laundering or terrorist financing. EDD may include obtaining additional information on the customer's identity, source of funds, business activities, beneficial owners, and expected transactions. Details on individuals with control over the account are relevant for EDD, as they may indicate the involvement of politically exposed persons (PEPs), sanctioned individuals, or other high-risk entities. Therefore, this information should be gathered as part of EDD for a high-risk customer.