第40 至 43 題為題組 The planet’s deepest point is in the Pacific Ocean’s Mariana Trench, which lies miles below the seasurface. According to a new study published in Nature Ecology & Evolution, even in this remote locale,creatures cannot escape pollution.      A team of researchers recently sent a remotely operated vehicle into the depths of the Mariana Trench.They found that extraordinarily high levels of forbidden industrial chemicals are contaminating marine lifemore than 7 miles deep in the trench. The small hard-shelled marine life that the robotic submarine broughtto the surface was polluted with toxic chemicals, with toxin levels 50 times greater than those of the mostheavily polluted rivers in the world.    These pollution levels were not the only alarming aspect of the discovery. The types of compoundsfound were all considered “persistent organic pollutants” (POPs), meaning they stick around in theenvironment for a very long time. Two of the most prevalent types are PCBs and PBDEs. PCBs were onceused in many industrial applications, but were outlawed in the United States in the 1970s after being linkedto cancer. Similarly, PBDEs were used in a wide range of products—from electronics to couch cushions.Neither chemical breaks down in the environment.   These compounds stick to the surface of materials like plastic. Many creatures mistakenly eat thiscolorful but toxic material, causing the POPs to build up in their bodies, lurking in their fat tissues. Whenthese sea creatures die, their POP-riddled bodies sink to the ocean floor, where deep-sea marine life eattheir remains. POPs are therefore transferred to other creatures along the food chain.   The Mariana Trench is many miles away from any industrial source. This suggests that these pollutantstravel over long distances despite having been prohibited worldwide decades ago.
40. What is the passage mainly about?
(A) The decrease of polluted creatures in the food chain.
(B) Using remote control in research on marine pollution.
(C) Pollution of the deep sea by persistent toxic chemicals.
(D) Types of chemical pollution caused by industrial applications.