Number of stereo center and stereoisomer of the given compound :
(a) 1 and 2         
(b) 2 and 4
(c) 3 and 8
(d) 3 and 6

No of stereo isomers = 2^n
n is the number of chiral atoms
Chiral atoms are bonded to four different groups
check the attached image :
3 stereocenters and  2^3 is the number of stereoisomers .

OK i understood (C) is correct answer thanks mam.