The solution which has the lowest freezing point temperature is one which has the highest depression in freezing point ( ΔT
The depression in freezing point is a colligative property and depends on the number of solute particles. Greater is the number of solute particles, greater is the depression in the freezing point.
I would say the solution a because in the winter when it’s snowing they usually put salt which is NaCl on the road so it gets less slippery and i guess that’s why
