臭氧在距地球表面12至30英里的地方形成一个保护层。

Ozone forms a protective layer between 12 and 30 miles above the Earth's surface.

《柯林斯英汉双解大词典》

然后会再洒上少量尘土，在皮肤上形成一个尘土的保护层(大象也防晒吧！)

Then they often follow that with a sprinkling of dust to create a protective layer of dirt on their skin (think elephant sunscreen!)

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生锈的表面形成一层防水保护层。

The rust forms a weatherproof layer of protection.

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