Hello,

According to the pass criteria for class 12 in the CBSE official site,

replacement of subjects is possible only for electives. This means, if you fail an elective subject, then an additional elective subject can take that place and you can pass.

But History is your core subject. It is mandatory to score 33% marks in the external exam of History for you to pass.

Don't worry in many cases, the secured marks are greater than expected marks because of various procedures like grace marks and moderation between sets.

Hope this helps.

Thanks.