单选题 According to the passage, rain prediction requires a quantitative description of droplet collision 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.