问答题

Pollution is caused either by man’s release of completely new and often artificial (人造) substances into the environment, or by releasing greatly increased amounts of a natural substance (物质), such as oil from oil tankers into the sea.

【参考答案】

有两种情况可以造成污染。一是人类向周围环境排放新的人造物质；二是排放大量的天然物质，如油轮在海上发生泄油事件。

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