According to the passage, rain prediction requires a quantitative description of droplet c

ollision in turbulence for which of the following reasons？

A．The "sling effect" remains unproven and requires experimental corroboration.

B．The degree to which droplets collide is the only reliable method of assessing air flow.

C．The degree of turbulence may help forecast the formation of large-size droplets that precipitate rain.

D．Such factors as warm and cold fronts and individual cloud formations could not be performed otherwise.

E．The laws which govern the formation of concentration heterogeneities still need to be discerned.