Resposta :
If it snows, people wear warm clothes.
Zero Conditional
I just don't see any mistake in the 3rd one, but I couldn't find its rule, I haven't found any conditional, so I think the 2nd one is sort of "correcter".
If it wasn't what you were looking for, I'm sorry perhaps I didn't understand well what did you mean.
Hope I've helped, enjoy your studies.