The Financial Action Task Force (FATF) Recommendation that should cause an anti-money laundering specialist the most concern is B: Financial institutions should not keep anonymous accounts. This is because anonymous accounts are accounts that are opened or maintained without verifying the identity of the customer or the beneficial owner, or with fictitious or incomplete information. Anonymous accounts pose a high risk of money laundering and terrorist financing, as they can be used to conceal the origin, destination, and purpose of illicit funds, and to evade the detection and reporting of suspicious transactions. Therefore, the FATF Recommendation 10 requires financial institutions to identify and verify the identity of their customers and the beneficial owners, and to prohibit the opening or maintaining of anonymous accounts or accounts in obviously fictitious names1.
The other options are also FATF Recommendations, but they are less relevant or applicable to the scenario.
Option A: Financial institutions should not warn their customers when information relating to them is being reported to the competent authorities, is the FATF Recommendation 21, which aims to prevent tipping-off, i.e., alerting the customer that they are being investigated or reported for money laundering or terrorist financing. However, this does not directly address the issue of identity verification or anonymous accounts2.
Option C: Financial institutions should maintain all necessary suspicious transaction report records on transactions, both domestic and international, for at least 5 years, is the FATF Recommendation 11, which aims to ensure that financial institutions have adequate and consistent records of their customers and transactions, and that these records are available to the competent authorities when needed. However, this does not prevent the opening or maintaining of anonymous accounts in the first place3. Option D: If financial institutions suspect that funds stem from criminal activity, they should be required to close the account, is not a FATF Recommendation, but rather a possible action that financial institutions may take in accordance with their risk assessment and policies. However, the FATF does not mandate or recommend the closure of accounts as a general rule, and advises that financial institutions should consult with the competent authorities before taking such action, as it may alert the customer or compromise the investigation4.
References:
1: FATF Recommendation 10: Customer due diligence, 1 2: FATF Recommendation 21: Tipping-off and confidentiality, 2 3: FATF Recommendation 11: Record keeping, 3 4: Frequently Asked Questions (FAQs) related to Suspicious Transaction Reporting, 5

According to the Basel Committee on Banking Supervision standards, the following statements best describe sound practices in relation to customer due diligence (CDD) policies and procedures:
Banks should take into consideration the occasional banking transaction or the size/level of assets to build an understanding of the customer's profile and behavior. This is because the nature and frequency of transactions and the size of the account balance may indicate the level of risk associated with the customer and the need for ongoing monitoring1 Banks should develop and implement clear acceptance policies and procedures to identify the types of customer that are likely to pose a higher risk of financing terrorism or money laundering. This is because banks should not enter into or maintain relationships with customers who pose unacceptable risks to the bank or the financial system. Banks should also apply a risk-based approach to CDD and apply more stringent measures to higher-risk customers12 Banks should implement enhanced due diligence measures for entering business relationships with high-risk customers, such as approval by senior management. This is because banks should ensure that they have adequate information and controls to manage the risks posed by such customers and to comply with the relevant laws and regulations. Senior management should be involved in the decision-making process and be accountable for the outcomes12 References: 1: Basel Committee on Banking Supervision, Consolidated KYC Risk Management, October
2004, page 6-7. 2: Basel Committee on Banking Supervision, Customer due diligence for banks, October
2001, page 8-9.

New business products should be evaluated for AML concerns before they are launched into the market. This is because new products may introduce new risks or vulnerabilities that could be exploited by money launderers or terrorist financiers. By conducting a pre-launch assessment, a financial institution can identify and mitigate these risks, design appropriate controls and procedures, and ensure compliance with the relevant laws and regulations. A pre-launch assessment can also help a financial institution to align its AML strategy with its business objectives, and avoid potential reputational damage or regulatory sanctions.
References:
9 Things to Consider When Evaluating an AML Solution
CAMS Study Guide 6th Edition, page 38.