It is a complicated problem.

这个问题错综复杂。

《新英汉大辞典》

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

This "turns out to be a much more complicated problem than we thought -but we know how to solve it", Dr Venter says.

这是“一个比我们所设想的复杂得多的问题——但我们知道如何去解决，”凡特博士说。

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

Now, as I said last time, the subject of free will--or free will, determinism, causation and responsibility, this cluster of problems-- is an extremely difficult and complicated physical problem.

正如我上次所说的,自由意志这个主题 或者说自由意志,决定论,因果论,责任,这一堆问题,是极端困难和复杂的物理问题

耶鲁公开课 - 死亡课程节选

This is so obvious in this problem, but when you see more complicated formula, you may not know all the assumptions that went into the derivation and quite often you will be using it when you shouldn't.

在这道题中这些都很明显,但是当我们用更复杂的公式时,你可能搞不清楚所有,在推导时的前提,因此很多时候,你都会用错公式

耶鲁公开课 - 基础物理课程节选

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