[单项选择]A "radiative forcing" is any change imposed on the Earth that affect the planetary energy balance. Radiative forcings include changes in greenhouse gases (such as carbon dioxide and ozone), aerosols in the atmosphere, solar irradiance, and surface reflectivity. A forcing may result from either a natural or an anthropogenic cause, or from both, as in the case of atmospheric aerosol concentrations, which can be altered either by volcanic action or the burning of fossil fuels. Radiative forcings are typically specified for the purpose of theoretical global climate simulations. In contrast, radiative "feedbacks" are environmental changes resulting from climate changes and are calculated from scientific observation. Radiative feedbacks include changes in such phenomena as clouds, atmospheric water vapor, sea-ice cover, and snow cover. 　　The interplay between forcings and feedbacks can be quite complex. For example, an increase in the concentration of atmospheric water vapor increases solar
A. forms one of anthropogenic causes of radiative forcings.
B. results in both radiative forcings and radiative feedbacks.
C. can hardly affect atmospheric forcings and feedbacks.
D. makes up a significant type of radiative forcing.