Sir i am good in objectives butcan't build proper interest for subjective papers how can i perpare properly for cbse 2015 paper?

you are good in objective ,it means that you are having a sound knowledge of concepts.Then,it should be easy for you to write also.The only thing lies is the practise.For this just solve the previous year paper and see the format of writing .Here you will be able to analyse yourself what to write according to the mark and time you should take.So I suggest you to write NCERT pattern answers,in other words answers written from NCERT textbooks