TOEFL Listening: TPO-TOEFL阅读TPO - HTD4BE77XJ1NRCY7N$

According to paragraph 1 all of the following are true of stream sorting EXCEPT A. Most of the particles in mountain streams pile up behind boulders and cobbles B. When particles of different sizes settle in a place, the smaller ones sit atop the larger ones C. There are generally more large particles upstream than downstream in a river. D. In some situations, downstream particles are created from rocks that eroded as they traveled downstream