The longest track and field event at the Summer Olympics is the 50-kilometer race walk, which is about five miles longer than the marathon.

夏季奥运会最长的田径项目是50公里竞走，比马拉松距离还长大约5英里。

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Now, the semifinal of the track and field event is underway.

现在，田径项目的半决赛正在进行。

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He is expected to deliver China's only gold-medal in the track and field event in the Beijing Olympics.

他预计交付在田径比赛的中国的唯一的金牌在北京奥林匹克。

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The example NBC used was watching the long jump and javelin at the same time as part of a track and field event.

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In another first, NBC Olympics Live Extra will provide multiple concurrent streams for select sports, such as gymnastics (each apparatus), track and field (each event), and tennis (up to five courts).

ENGADGET: NBC's 2012 London Olympics second screen and streaming apps for Android and iOS launch today

But the 24-year-old was pulled out of the event by USA Track and Field after his positive test at the US indoor championships in Albuquerque, New Mexico, on 28 February.

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