Hello Vaishali,

All the optional subjects mentioned in the UPSC notification are open to all the eligible students regardless of their bachelors subject. With regards to your bachelors' subjects, you can opt for any one of the three that is - Botany, Chemistry, and Zoology. These three are available in the list and if you want to take up your bachelors' subject as optional, you can go for it.

All the best.