TOEFL Listening: ETS-TOEFL听力机经 - O3A8H15P1NA33Y4RP$

According to the lecture, the uneven distribution of sediment on the seafloor is caused by which of the following? A. The ongoing generation of new seafloor at mid-ocean ridges B. Denser populations of microscopic sea life in certain areas C. Fragments of dry land dropping and settling on the ocean floor D. Oceanic currents that carry sand and stones up onto beaches.