题目内容

Air turbulence can substantially accelerate the appearance of large dropletstriggering rain by presenting a new mechanism, the "sling effect", whichincreases collisions of droplets that have become detached from the airflow.Line First, vapor condensation in cloud cores produces small droplets resembling one(5) another in size, which then expand to raindrop size by coalescing under theeffects of air turbulence—a force thought to cause collisions of similar-sizeddroplets whose radii exceed a few micrometers. Then, turbulent vortices act assmall centrifuges that spin heavy droplets out, creating concentrationheterogeneities and jets of droplets, both of which increase the mean collision(10) rate, which in turn accelerates rain initiation.One can conclude that rain prediction requires a quantitative description ofdroplet collision in turbulence, a mechanism which helps meteorologists toforecast rainfall, but detailed understanding of the phenomenon entailsconsideration of such factors as warm and cold fronts stretching over hundreds(15) of miles, individual clouds perhaps a mile or so across, and even, as themechanism illustrates, tiny eddies perhaps a few centimeters or so in size. According to the passage, air turbulence generally does which of the following Ⅰ. Creates small droplets of equal size to form in cloud cores.() Ⅱ. Causes different concentrations of rain droplets to form in different places. Ⅲ. Speeds up the rate by which large droplets appear.

A. Ⅰ only
B. Ⅱ only
C. Ⅰ and Ⅱ only
D. Ⅱ and Ⅲ only
E. Ⅰ, Ⅱ, and Ⅲ

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