answer would be D:
R1 is definitely partial order set (>= is classic example of poset)
R2 is clearly not reflexive therefore not partial order set
coming to R3 : we have to check whether it is antisymmetric or not: i.e (aRb and bRa) implies a=b
suppose we take +3 and -3 now (3)^{2} <= (-3)^{2 }and (-3)^{2} <= (3)^{2} implies that 3=-3 which is false therefore it is not antisymmetric in nature following not a partial order.