We know that oil can be a slow and silent killer.

我们知道，石油能成为缓慢而沉默的杀手。

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A silent killer lurks beneath the surface of this West African lake.

在这个西非洲湖泊的表面下潜藏着一个无声的杀手。

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It's sometimes called "the silent killer" because it has no symptoms.

它有时也被称为“沉默杀手”，因为它没有任何症状。

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Carbon monoxide is called the silent killer because people do not know it is in the air.

VOA: special.2010.02.02

Carbon monoxide poisoning is known as a silent killer.

VOA: special.2010.02.02

"Hepatitis B is the silent killer because most people who are chronically infected may not be aware of the infection."

VOA: standard.2010.07.26

The gas is known as the silent killer because it cannot be seen or smelt.

BBC: Carbon monoxide detector

Sedentary living is the most prevalent disease, biggest silent killer and greatest health threat facing developed countries.

BBC: Laziness will send us to an early grave

"A silent killer" - those are the words David Bull uses to describe his long-standing liver complaint.

BBC: Liver damage is 'silent killer' cirrhosis patient warns