No for jee u have to give improvement in all 5

Dear



If you have target for top engineering colleges then you should appear for all the subjects and through that not only improve your grades but it will give more chance to get seat in top engineering colleges.



All the Best

Improvement exams are provided(like the way you wanna give) only by some colleges and not by any state or central board for secondary education.

No you have to appear for all subjects in improvement examination......then your new percentage would be considered.....don't worry be focussed on your jee preparation....just give some time for boards also