Hello, Bihar Board will conduct the re-exam in the month of July 2019 and the compartmental result will be released in the month of August. After the declaration of Bihar Board 12th Result 2019 which is expected to be released today on March 30, 2019, student who wishes to apply for improvement can do so. You don't have to appear in all the subjects. You can choose the subjects with low scores or the subject failed.

Yes improvement exam can be given for subject where you scpred relatively lower than other subjects and wish to improve score of same. It can be only one or more than one as well.

No need to appesr for all subjects again in improving exam, only must go for subjects with compartment or with very low scores.