A. Quality Function Deployment (QFD)
B. Prototyping
C. Soft Systems Methodology (SSM)
D. Controlled Requirements Expression (CORE)

Explanation: Soft systems methodology (SSM) is a systemic approach for tackling real-world problematic situations.It is a common misunderstanding that SSM is a methodology for dealing solely with ‘soft problems’ (problems which involve psychological, social, and cultural elements). SSM does not differentiate between ‘soft’ and ‘hard’ problems, it merely provides a different way of dealing with situations perceived as problematic.