One useful method of process improvement involves consideration of how another organization performs a process, identifying and analyzing best practices for improvement ideas. this method is known as:

a. benchmarking
b. root cause analysis
c. comparative improvement
d. voice of the customer

a. benchmarking

Explanation:

Benchmarking is a management strategy that a  business uses to measure productivity, or set goals based on the industry's best practices. An organization applies the benchmarking approach to evaluate its quality, processes and procedures, and performance against that of other firms. An organization uses the benchmarking report to improve its operating and product standards.  

Benchmarking can be internal or external. Internal benchmarking involves comparisons between teams, departments, or individuals within an organization. External benchmarking is where a firm gauge its critical operations against those of its competitors or other similar companies.