When the sky is cloudy in summer, the temperature during the day will not be too high. Among them, () A. Water vapor and carbon dioxide B. Clouds and dust C.

A, water vapor and carbon dioxide absorb infrared rays with longer wavelengths, so it does not meet the meaning of the question;

B, clouds and dust reflect solar radiation, so it is correct;

C, ozone can absorb a large number of short-wavelength ultraviolet rays, so it does not meet the meaning of the question;

D, air molecules and tiny dust scatter solar radiation, so it does not meet the meaning of the question.

Therefore, choose: B.