The smoke produced by Xiao Ming's father smoking contains a lot of toxic substances, such as carbon monoxide and nicotine. Because the particles that make up these substances are constantly moving and diffuse into the surrounding air, it will cause others to smoke passively, which is often called second-hand smoke. Passive smoking has nothing to do with molecular size, molecular spacing and intermolecular interaction, so A, B and C are wrong and D is right.
So choose D.