Strategy for exam

Dear sir, actually I have struggled with question in part C.I have 1 idea that I will concertrate on part A and part B.I will be allowed to be wrong in 2 questions in part A which are often difficult as comment in examiner report and 3 questions in part B,I suppose that there is 1 difficult question in 1 topic of part B.In part C, maybe there is easy mark or question regarding to the calculation.I will try to have 5 mark in part C.Total I have enough mark to overcome.Do you think it is a acceptable idea? Since it takes me a lot of time to deal with question in part C in the past exam.And the question in each year is not same.Please give me an advice.Thank you.