You must also have mathematics exam in your syllabus as NDA exam includes MATHS as well. And your concepts of 11 and 12th Maths must be good enough so that you tackle the questions well.

Since you are a PCB student, science part should not be much difficult for you and you must be thorough with your PCM syllabus so that you do well in this section as well.

The next section is English and Grammar, along with studying PCB, some days you can do Grammar skills also. You can refer books like Wren and Martin.

For General Knowledge, you've to read a lot and also have latest updates, reading newspapers will also help you decently.

You have to be very choosy with your books and have to select the best books. For Maths you can use NCERT books, ES Ramasamy, and Pathfinders.

For English, Nithu Singh and SP Bakshi are decent books.

For General Knowledge, you can use Lucent Publications and NCERT books.

Refer the link below for a more detailed information..

https://competition.careers360.com/articles/how-to-prepare-for-nda

Best wishes. Thank you.