What is the difference betwee a restrictive and a non restrictive clause

the choice that is not a technique that you should use to come up with ideas for the topic of a research project is, writing about academic subjects that are not interesting to you. this does not belong to the techniques to come up with ideas because having no interest in a certain topic will lose your drive to come up with better ideas. it gives no room for improvement and acquiring of new ideas and information. 

explanation:

the correct answer is:   [c]:

                    →     " leave it out. "  

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