Final answer:
The key ethical concern for HR is understanding the business case while minimizing impact on affected employees, ensuring transparent communication, and providing adequate support during the transition.
Step-by-step explanation:
The most important ethical concern for HR in the planning and implementation processes of moving a manufacturing unit is C. Understanding the business case for the initiative and minimizing impact on affected employees. This includes taking into account the ripple effect of job losses and relocations, the resultant frictional unemployment, and ensuring that ethical and transparent communication with affected employees takes place. Additionally, HR should be involved in supporting and advising on relocation efforts and updating job descriptions, but these actions need to be underpinned by a strong ethical commitment to the well-being of the company's employees.