hi,

bachelor of science is 3 years course which is open distance learning course. now see IGNOU has many regional centers as per state wise, so the subject combinations are available in regional centers for the reference study purpose and materials for studies. however in official site of Ignous has mathematics, chemisty, geology and physics materials. yes you are eligible to take the combinations as per your interest. you may contact with the nearest regional centers for more clarity in this matter.

follow the below link to get details on regional centers.

https://ignouadmission.samarth.edu.in/index.php/site/programme-detail?id=8f25855181c6d3ad733a52630bc62a70abe9f124f7260f623452fbfae3c99b181155