Dear Pritam ,

Look, The actual meaning of Additional and Optional is more or less same . But the little difference is ,

• In Optional Subject, you must choose one subject from the given available subjects as per your stream i.e Science , Arts or Commerce
• In Additional Subject , you need to choose an extra subject apart from your regular curriculum .

Generally , in Madhyamik Exam, conducted by WBBSE .. This '' Additional" term is used as in that case , you may or may not choose your additional subject . It will not  effect your total score in Madhyamik.

But , in HS .. The best of 5 Policy is accepted . So in that case , you need to choose One optional Elective paper from the given subject list as per your stream as said earlier above.

Some more information about HS Exam :

• It is Conducted by West Bengal Council of Higher Secondary Education
• Once in A year
• Board exam for class 12 Students
• you can also check prev year HS questions from here : https://school.careers360.com/boards/wbchse/wbchse-question-paper

Hope this helps !