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1. 除此之外，有些办公室允许吸烟，也是一大污染源。

   chú​cǐ​zhī​wài, yǒu​xiē bàn​gōng​shì yǔn​xǔ xī yān, yě​shì yī dà wū​rǎn​yuán.

   In addition, some offices allow smoking, which is also a major source of pollution.

   Source: CCMatrix