The second source of carbon dioxide lies outside Europe.

第二个二氧化碳的来源在欧洲之外。

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There could also be good news for transport, the next biggest source of carbon emissions.

对于运输—二氧化碳排放的第二大来源，也是好消息。

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Steel is an alloy of iron and carbon. Coking coal is a source of carbon in the smelting process.

钢是铁与碳的合金，焦煤便是熔炼过程中碳的来源。

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There could also be good news for transport, the next biggest source of carbon emissions.

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