Hello , 

As your query is you want to reappear in the CBSE examination that is going to held in 2020 in all the 5 subjects as you failed in one subject only. 

I would like to tell you that as your issue is concerned definitely you can apply for the examination as a private candidate. And eventually that would be better because you will get a plenty amount of time to prepare and look over for other entrance exam as a further option in career. 

Further, if you have any other query regarding the same you can let me know in the comment section below.

I hope your query is solved.

Thank you.