It's not high mountains and deep valleys that best serve to defend a country.

固国不以山溪之险。

《新英汉大辞典》

Heavy eyebrows, facial hair and deep voices all could serve to make a man more imposing to other men.

浓眉、胡子和低沉的声音都能使一名男子比其他男子更显气概。

youdao

We don't serve God out of guilt or fear or even duty, but out of joy, and deep gratitude for what he's done for us.

我们服侍神，不是出于罪疚感，恐惧，也不是因为责任，而是出于喜乐，出于深深的感恩，感谢神为我们所作的一切。

youdao

The roof now closed because of rain, Djokovic, by now taking an age to deliver each serve, dug deep to hold his next service game, but Berdych's double-fisted backhand was beginning to yield results.

BBC: Novak Djokovic makes short work of Berdych in Melbourne

The system he created and the worlds that came out of it are deep, interesting and serve as valuable tools for people to learn many different things about themselves, their lives and the reality.

BBC: Role-playing games pioneer dies

Critics warn that many of these new developments will only serve a tiny elite, exacerbating an already deep divide between the haves and have-nots.

CNN: Africa's 'new cities': Urban future or utopian fantasies?