Wuhan smog weather app

A. Smog is a big dust particle and a solid substance; Instead of a large number of small water droplets or ice crystals floating in the near-surface air layer; So, A is wrong;

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

C, the essence of fog is small water droplets, and the essence of haze is small solid particles; So fog and haze are two different concepts; So, c is wrong;

D, fog is water vapor in the air, which liquefies into liquid when it is cold; So, d is wrong;

So choose B.