As per current pattern one has to choose two optional for IFoS. Each of them have two paper of 200 marks each. This means both optionals together form a total of 800/1700 in your final score
From the notification, the options to choose optional are –
- (i) Agriculture
- (ii.) Agricultural Engineering
- (iii) Animal Husbandry & Veterinary Science
- (iv) Botany
- (v) Chemistry
- (vi) Chemical Engineering
- (vii) Civil Engineering
- (viii) Forestry
- (ix) Geology
- (x) Mathematics
- (xi) Mechanical Engineering
- (xii) Physics
- (xiii) Statistics
- (xiv) Zoology
- (a) Agriculture and Agricultural Engg.
- (b) Agriculture and Animal Husbandry & Veterinary Science.
- (c) Agriculture and ·Forestry.
- (d) Chemistry and Chemical Engg.
- (e) Mathematics and Statistics.
- (f) Of the Engineering subjects viz. Agricultural Engineering, Chemical Engineering, Civil Engineering and Mechanical Engineering- not more than one subject;
My 2 cents – choose your optional wisely. As far as possible – Forestry should be one of the optional. This is because if you prepare it beforehand, it will help you in prelims (environment portion), CSE mains (allelopathy type question in GS3 – 2016 paper), IFoS interview (they are definitely going to ask something from forestry even if you dont have it as an optional)