Explanation:

• Option A (Correct): Cluster sampling involves dividing the population into clusters, each representing a mini-version of the entire population. Certain clusters are then selected entirely using simple random sampling. This method is particularly useful for market surveys, where clusters are often defined by geographic parameters.

• Option B (Incorrect): Auditing financial statements typically employs judgmental sampling, where elements are selected based on the auditor's expertise and professional judgment, rather than cluster sampling.

• Option C (Incorrect): Constructing a bond portfolio to mirror an index is an application of stratified sampling, not cluster sampling. Stratified sampling is commonly used in bond indexing to ensure the portfolio reflects the index's performance accurately.