Hii Abhishek,
F.I.T and hindi/sanskrit is your optional subject.
It depends on how you perform in the board examinations. It is not necessary, as far as you paas in the board's five main subjects, i.e., two languages, mathematics, science, and social science.
But if you fail in any of the three elective subjects, i.e., mathematics, science, or social science, it will be replaced by the 6th subject you have opted. If such is the case you definitely need to pass in the 6th subject as well.
Hope it Help !!!