I was astonished by the size and complexity of the problem.

这个问题的复杂性和涉及面之广使我感到惊讶。

《牛津词典》

They are aware of the complexity of their problem domain, and the need for a multi-disciplinary framework to solve said problem.

他们意识到自己问题领域的复杂性，并知道要利用多学科框架来解决上述问题的需求。

youdao

Cease believing that a single country or a small group of countries can solve a problem of such complexity.

停止幻想一个国家或者一小撮国家可以解决这样复杂的问题吧。

youdao

And he committed himself in the coming weeks to taking steps that use the power of his office to help try to bring about changes that will address this problem, recognizing the complexity of the problem and the obstacles to potential solutions to the problem.

WHITEHOUSE: Press Briefing by Press Secretary Jay Carney,

The main problem is that the complexity of computer networks makes it very difficult to quantify risk accurately.

ECONOMIST: Putting it all together

The problem has been the sheer complexity of the data and the ensuing processing and analysis of the information.

BBC: World's most detailed scans will reveal how brain works