It is a complicated problem.

这个问题错综复杂。

《新英汉大辞典》

This is quite a complicated problem and one which is difficult to solve.

这是一个相当复杂的问题，这是一个难以解决的。

youdao

It's a complicated problem, because the echoes from all the different layers of rock interfere with each other.

这是一个复杂的问题，因为来自不同的岩石层的回声相互干扰。

youdao

But when Suzuki ran for re-election two years ago, he ran into a problem a complicated election law that bans Internet use during the campaign season.

VOA: standard.2009.07.27

Hobrooke admits is a very complicated and difficult problem to address.

VOA: standard.2009.06.15

So we're quite pleased to have a dedicated facility, and that's a complicated problem.

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If a patient has a complicated problem, volunteer specialists and hospitals donate their services.

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The development of the Tethyan Realm is such a complicated problem that it remains far from being clarified.

UNESCO: EARTH SCIENCES FOR SOCIETY