how to start an answer?

Although many questions can be answered using 'common sense' this is not an exam in common sense. It has a syllabus with many theories and models quoted. Therefore, when you answer a question, try not to answer it 'in general'. Try to support your answer with a theory (or two). Obviously, if you can't think of a theory, answer it as best you can.

However, do not describe theories unless you were specifically asked to. In this exam the emphasis is on using the theories to solve the problems described in the scenarios.

As for starting, if you have trouble, write your first sentence so as to define an7y technical term used in the question. So, if the question says "Identify and describe the importance of the organisation's stakeholders", start of your answer with something like "A stakeholder is any person affected by the organisation." Don't go into huge description, because you were not asked to define 'stakeholder' however, starting like this can focus your attention and break the terror of the blank page.

HTH