The primary reason to perform a risk assessment is to determine the current risk profile of the organization, which is the level of risk exposure and the likelihood and impact of potential threats. This will help the organization to identify and prioritize the risks that need to be addressed and to align the risk management strategy with the business objectives. A risk assessment may also help to achieve compliance, support the BIA, and allocate budget, but these are not the primary reasons. References: ISACA Glossary of Terms, section "risk assessment"

The major advantage of automating internal controls is to efficiently test large volumes of data, because automated controls can perform repetitive tasks faster, more accurately, and more consistently than manual controls. Automated controls can also provide audit trails and exception reports that facilitate the monitoring and evaluation of the control effectiveness12. Reviewing large value transactions, identifying transactions with no segregation of duties, and performing analytical reviews are possible benefits of automating internal controls, but not the major advantage. References: 1: CISA Review Manual (Digital Version), Chapter 5, Section 5.2.2 2: CISA Online Review Course, Module 5, Lesson 2

Substantive testing provides the most reliable audit evidence on the validity of transactions in a financial application. Substantive testing is an audit procedure that examines the financial statements and supporting documentation to see if they contain errors or misstatements. Substantive testing can help to verify that the transactions recorded in the financial application are authorized, complete, accurate, and properly classified.
Substantive testing can include methods such as vouching, confirmation, analytical procedures, or physical examination.

Access authorization tables are the best way to achieve effective separation of duties in an online environment, as they allow the definition and enforcement of different access rights and privileges for different users or roles, based on the principle of least privilege12. Access authorization tables can help to prevent unauthorized or inappropriate actions, such as fraud, errors, or misuse of the system, by ensuring that no user has enough privileges to perform all parts of a transaction or business process34.
References
1: Separation of Duty (SOD) - Glossary | CSRC3 2: Separation of Duties within Information Systems4 3:
Separation of Duties: Implementation & Challenges in IT2 4: Implementing Segregation of Duties: A Practical Experience Based on Best Practices - ISACA1

Multi-tenancy within the same database (B) presents the greatest risk of data leakage in the cloud environment, because it means that multiple customers share the same physical database and resources. This can lead to data isolation and security issues, such as unauthorized access, cross-tenant attacks, or data leakage due to misconfiguration or human error. To prevent data leakage in a multi-tenant database, cloud providers need to implement strict access control policies, encryption, isolation mechanisms, and auditing tools.
Lack of data retention policy (A) is not the greatest risk of data leakage in the cloud environment, because it mainly affects the availability and compliance of data, not its confidentiality or integrity. Data retention policy defines how long data should be stored and when it should be deleted or archived. Without a data retention policy, cloud customers may face legal or regulatory issues, storage costs, or performance degradation.
Lack of role-based access is not the greatest risk of data leakage in the cloud environment, because it can be mitigated by implementing proper authentication and authorization mechanisms. Role-based access control (RBAC) is a security model that assigns permissions and privileges to users based on their roles and responsibilities. Without RBAC, cloud customers may face unauthorized access, privilege escalation, or data misuse.
Expiration of security certificate (D) is not the greatest risk of data leakage in the cloud environment, because it can be easily detected and renewed. A security certificate is a digital document that verifies the identity and authenticity of a website or service. It also enables secure communication using encryption. If a security certificate expires, it may cause trust issues, warning messages, or connection errors, but not necessarily data leakage.
References:
7 Ways to Prevent Data Leaks in the Cloud | OTAVA
An analysis of data leakage and prevention techniques in cloud environment