How to Attempt Such a Lengthy Question like this in Exam

Dear Tutor,

Hope you are doing good. Actually I wanted to ask you that what’s the best possible way which gets you the max marks possible in the time limit of attempting a lengthy and time pressured question like June 2011 Q3 YNM part a for 13 marks but whose every single requirement I think cannot be answered in full satisfactorily in the 20 mins time limit because in my opinion its requiring too much in too little time. In short how would you attempt this question in exam to get the max possible marks?

Thank you.