Hello Nipun, See if date and Time is Same then nothing can be done... You have to skip one...

 In my personal opinion go for Amrut entrance test. NDA exam happens twice in a year. You can reappear NDA in coming months... So, All the best

These are some of the books..

Pathfinder for NDA & NA Entrance Examination

For GK- Manorama Yearbook 2015 by Mathew M is Best.

Mathematics for NDA and NA: National Defence Academy and Naval Academy by R S Aggarwal

Objective General Knowledge & Current Affairs (Level 1) : Useful for UPSC

Hello Kanishka, Its True for Indian army exam conducted by UPSC and candidate need to crack CDS (Combined defense services) exam held for NAVY, MILITARY and AIR FORCE. successful CDS candidate shortlisted for SSB (staff selection board) for the interview...

YOU should also know that there are 3 ways a

 check the eligibility criteria of NDA

fill the application form may notification will be on june 2018

Check complete details on How to Join NDA after 12th

Also read-

NDA Eligibility Criteria

NDA Application Form

NDA Cut off

NDA Selection Process

How to prepare for NDA?

Particularly for Biology student there is no specific career in NDA but if you have completed 12th with Physics, Chemistry and Mathematics along with Biology then you can apply for Indian Navy/Air Force in NDA and if you're really interested in Biology, complete your MBBS first, then you can

NDA is for all streams, A candidate who is graduate in any stream can apply for this. Incase of TES, a candidate need to have graduation in engineering or technical stream say B.tech 

To crack NDA, one need to clear written exam and SSB but for TES, candidate can directly

Dear Arpit,

In order to be eligible for NDA your minimum age should be 16.5 years and maximum age should be 19.5 years. 

You can check the educational qualification below

Army Wing: Candidates applying for Indian Army must have passed class 12/HSC in 10+2 pattern of School Education or equivalent

In order to apply NDA Entrance exam for Navy Soldier you must have passed class 12 with 10+2 pattern of school education or equivalent examination with Physics and Mathematics by a State Education Board or a University and you must be between 16.5 and 19.5 years of age. You can

NDA consists of written exam and if you clear NDA exam then you are eligible to sit in 5 days SSB 

Interview.

Once you clear SSB interview and get recommended you will have one medical test.

After clearing medical test then you will be in NDA.

For more info read