Hello,
Unfortunately, you can't give compartment exam in two subjects. Even if you have 6 subjects you can choose to appear in only one of them.
In your case, for compartment you can either appear for Physics or Chemistry. For other subjects you have to appear in next year board exam that is March 2021.
You can check more about this from official site of CBSE by clicking here - http://cbse.nic.in/examin~1/scheme06ex.htm
Hope this was helpful
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