I have been saying the same thing since last year on the forum that chemistry paper is not the thing to be opted in CSS, its paper pattern is typical consisting many parts from various areas. I'll suggest you all that please avoid to opt chemistry if you want to go for selected study as it needs a lot of time and selected study can ruin your score. Chemistry was the only subject where I was unable to solve all the questions last year so I am expecting lowest marks in chemistry.

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Your attitude, not your aptitude, will determine your altitude...Zig Ziglar