2. 外语
  3. Pollution occurs whenever unnatural substances are introduced into an environment. Most ocean pollution caused by humans are co

Pollution occurs whenever unnatural substances are introduced into an environment. Most ocean pollution caused by humans are co

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问题     Pollution occurs whenever unnatural substances
are introduced into an environment. Most ocean
pollution caused by humans are concentrated along the 【M1】______
coasts of continents. Let’s see what some of the pollutants are.
    Industrial wastes sometimes get to seawater. Often, 【M2】______
these contain(concentrations)of metals and chemicals
that harm organisms. Solid wastes, such as plastic bags
and fishing line left lying on the beaches, can entangle
in animals. Medical waste such as needles, plastic 【M3】______
tubing, and bags are a threat to both humans and
animals.
    Pesticides, which include herbicides(weed killers)
and insecticides(insect killers), used in farming
reaching the ocean as runoff. They become 【M4】______
concentrating in the tissues of marine organisms. 【M5】______
    Crop fertilizers and human sewage create a
different kind of problem. They fertilize the water. This
causes some types of algae to produce very rapidly. 【M6】______
When these algae die, they’re decomposed by huge
amount of bacteria. The problem is that the bacteria use 【M7】______
up much of the oxygen in the water during respiration.
However, other organisms such as fish can’t get the 【M8】______
oxygen they need, and they die.
    Oil spills also pollute the ocean. You’ve heard in
the news about major oil spills caused to tanker 【M9】______
collisions, and leaks at offshore oil wells. Another
source of oil pollution is oil mixed with wastewater
that’s pumped out of ships. In addition to these
resources, oil discarded from cars and industries is 【M10】______
sometimes dumped into streams. It, too, eventually
reaches the ocean.
【M9】
选项
答案to—by
解析 介词错误。原句的意思是“油轮碰撞导致石油泄漏”，显然to不合适。
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