These flow features are extensive systems—sometimes hundreds of kilometers in total length—of interconnecting, twisting channels that seem to merge into larger, wider channels.

拥有庞大的系统是径流渠道的流动特征——有时总长达数百公里——这些系统由蜿蜒交错的渠道组成，而且这些渠道可能会并入更长更宽的渠道。

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The researchers were able to send a total of 1 terabit of data 40 kilometers.

CNN: THE INTERNET

But the relative proportion of total fuel use can be extrapolated by comparing passenger kilometers traveled versus tonne-kilometers for freight on the top 10 carriers.

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The total polluted area is about 40, 000 square kilometers.

WHITEHOUSE: President Obama Makes a Trilateral Announcement with the Presidents of Russia and Kazakhstan | The White House