The correct answer is: A. Comparative analysis.
Comparative analysis is a technique of management audit in which functions and achievements of two or more firms are compared. It is a useful tool for identifying areas where a firm can improve its performance.
B. Inter-firm comparison is a type of comparative analysis that compares the performance of two or more firms in the same industry. This can be a useful tool for identifying best practices and benchmarking performance.
C. Routine check is a type of audit that is conducted on a regular basis to ensure that a firm is in compliance with regulations and procedures. This type of audit is not typically used for comparative analysis.
D. Ratio analysis is a technique that uses financial ratios to compare the performance of a firm over time or to compare the performance of two or more firms. This type of analysis is not typically used for comparative analysis.