Hi Sandep Kumar. The question you have asked is incomplete. Finish the question properly so that we can help you with it.

You will be checked on your fundamentals of English like your knowledge of English Grammar, Comprehension, etc. The topics you might have to study would be Grammar and Usage, Error Findind, Synonyms and Antonyms Word Pairing, Comprehension, Vocabulary, One word substitutions and Fill ups. Read articles from time to time. Follow newspapers, magazines, and watch the news channels and browse the internet to keep yourself updated. You will need a lot of reading to help you in the comprehension section. You will need speed to help you in this section and you can achieve that only by thorough practise and reading. Take time to understand the question because most answers are interlinked. These books should help you:

• Word Power Made Easy (by Norman Lewis)
  This is the go-to book to improve your vocabulary. It is not a book to be read but a book to work with daily to enrich your vocabulary.
  
  High School Grammar and Composition( by Wren and Martin)
  It is a very good book for people who want to improve their grammar skills. It helps to understand and conceptualise different aspects of grammar and it is a must have book for anyone with poor grasp on verbal ability or who wants to make up with the basics of English.

Lucent General English, Lucent General Science and General Knowledge are good resources to prepare for NDA examination, going through them thoroughly might give a cutoff clearing score. You must prepare for Mathematics very well, 12th level mathematics is sufficient, scoring good in Maths section will give a boost to your overall score. Also English of 10+2 is enough for NDA written test, main factor is to attempt GAT. You may also check out NDA Pathfinder

Hello! Hope you are doing good

You can end up doing graduation in computer science because then there are certain posts in railways for which this degree is a must. If you like sociology then you can continue with that or even take life sciences in graduation as a subject if you like environmental education. if you like drawing then you can even take painting as a subject and carry on with your work. What career opportunities you have depends on what you would like to do.

All the best

Hello

You can go through the link below and download the Model Question Papers
( Previous Year Question Papers) of Madras university:

https://egovernance.unom.ac.in/qpregular/question_main.asp

Good Luck!