Which solution would have the lowest freezing point?

a) 10g of MgCl2 dissolved in 100ml of water
b) 10g of sugar (C^12H^22O^11) dissolved in 100 ml of water

CHOICES
1) a because magnesium chloride is ionic and it forms 3 ions
2) a because magnesium chloride is covalent and it forms 3 ions
3) b because sugar is ionic and it forms one big molecule
4) b because sugar is covalent and it forms 3 ions​