The answer to this question would be b.
3 things affect the freezing point of water, a constant(Kf), molality(b) and a number of dissolved particles (i).
Kf is a constant so that has the same effect. Because you have 1 mole of everything, molality is also constant.
so the only thing you gotta look after is the number of the dissolved particles which which iron III chloride has the highest
