Three of the following are internal/external causes of organisational change, which is not A. People B. structure C. Process D. Departments

Thank you for the invitation, but I may understand your question on many different ways, and for which way I will come with a different answer. However, I may say all except people: organisational change may include the company's structure including the departments and of course the internal processes and procedures.

I can agree with Mr.Hussein's answer

Organization as a system, consists:

• People
• Structure
• Process

Agreed with the given answer. People are excluded if we talk about Organizational Change. 

D. Departments is the answer.

The organizational structure is an integrated whole, employees, departments, divisions, and the volume of operations, change is when it gets includes all these elements.

Regards.