Understanding of haze weather

A, the essence of smog is small solid particles; Not small water droplets and small ice crystals; So, A is wrong;

B, fog and haze are two different weather phenomena, the essence of fog is small water droplets, and the essence of haze is small solid particles; Therefore, B is correct;

C, fog is the water vapor in the air liquefied into liquid water droplets when it is cold; So, c is wrong;

D, fog and haze are not the same concept; So, d is wrong;

So choose B.