Explanation:

- Option 1: A substantive law

- Defines rights and duties.

- Governs the legal relationship and duties of individuals.

- Not directly concerned with the process of enforcing the law.

- Option 2: An adjective law

- Also known as procedural law.

- Prescribes the methods of enforcing legal rights and duties.

- Guides how a legal process unfolds and how evidence is presented.

- Option 3: Both (a) & (b)

- Suggests the law of evidence has elements of both substantive and procedural nature.

- Not applicable as law of evidence mainly concerns procedures.

- Option 4: Neither (a) nor (b)

- Implies the law of evidence is neither substantive nor procedural.

- Incorrect as it clearly pertains to legal procedures.

The correct answer is: Option 2: An adjective law