After the second explosion, all of London's main train and subway stations were shut down.

第二次爆炸后，伦敦所有的主要火车站及地铁站都被关闭了。

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Sebti saw a man bleeding from the chest and stooped to treat him when the second explosion occurred.

赛伯提看到一个男人的胸口正在流血，他就弯下腰去为他治疗，这时发生了第二次爆炸。

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In order to make a nuclear explosion, the critical mass must come together within a fraction of a millionth of a second.

为促成一次核爆炸，临界质量必须在一百万分之一秒内聚集在一起。

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The explosion was the second at the same market in 10 days.

VOA: standard.2009.06.01

Running toward the finish line, Erik Savage turned and ducked when he heard the second explosion.

NPR: The Finish Line: What The Bombing Was Like

The second explosion happened metres from where a man was standing talking on his on mobile phone.

BBC: Pimlico pavement explodes, narrowly missing passer by

It is still resonating when the second explosion comes and then the third.

CNN: Books - Excerpt: 'Flint'