changing optional. need help.

i have to change it. 

how should i decide which is suited for me. 

are there any optionals which are so called evergreen in terms of marks.(not too much variation in marks)

which ones help in GS prep most? also the best institutes of these. i have following choices: pubad, psir, anthro,socio. 

if there is any other which is considered doable,let me know.

it will be of immense help.

as of now ive no guidance and i dont know which direction to go for.

thanks in advance.