Hi Aspirant,

If are going to give KVPY SA, then yes it is compulsory and leaving biology section will cost you marks. But if you are giving KVPY SX/SB, then you're allowed to choose subjects and you can conveniently leave biology or any other section you wish to. Basically in the Stream-SA  all questions are compulsory. In respect of the streams SB and SX , candidates  may answer any three of the four subjects in Part I and any two of the four subjects in Part II. In case candidate attempts more sections, best of three in Part I and best of two in Part II is considered.

For more information regarding KVPY 2021 refer the link below,

https://school.careers360.com/exams/kvpy

Hope this is resourceful.

Best of luck!!!