We need clean air, but unfortunately, air pollution is generally present, especially in cities。

我们需要清新的空气，但遗憾的是，空气污染普遍存在，在城市中尤其如此。 [分析] 本句为了避免“尤其是在城市里”的表达不完整，增加了“如此”。

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Algae are an attractive way to harvest solar energy because they reproduce themselves, they can live in areas not useful for producing food and they do not need clean or even fresh water.

藻类由于能自行再生，是采攫太阳能的一种很有吸引力的方法，它们可以生长在无利于生产粮食的地方，不需要清水甚至淡水。

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"And we need to clean up so that they can come and build new residential places for our families here."

VOA: standard.2009.10.04

I just need to clean the dishes, before I come over.

在我来之前，我还得把盘子刷了。

I will实战 - SpeakingMax英语口语达人

Responding to the need for safe, clean and affordable lighting, Irvine-Halliday set to work on a solution.

VOA: standard.2009.12.13

People need it to drink, and they also need clean water to wash their hands.

FORBES: Clean Water Will Be Vital In Japan

We need clean water not only to sustain ourselves, but also for other basic necessities such as farming and sanitation.

FORBES: Investors Are The Key To Solving The World's Water Problems

We need clean coal in the U.S., and melding the technology with oil recovery is a smart way to make it economic.

FORBES: Sinopec's Clean Coal Plan Shows It's Set To Buy Chesapeake's Texas Oil Fields