The class remained dumb when the teacher asked a formidable question.

类当老师问一个令人生畏的问题保持沉默。

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Several answers have been proposed to address this fundamental question, but none has been proven-and even adequately testing them has proven to be a formidable challenge.

已经有几个答案被提出来来回答这个基本问题，但是没有一个被证明——甚至对它们的充分的检验也被证明是一个可怕的挑战。

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Drilling hole slanting question is a quite complex question in the drilling technology. Hole curving is a difficult technical problem and a formidable matter regarding us which is urgent to solve.

孔斜问题，在钻探技术上是一个比较复杂的问题，孔斜这一课题对于我们是一个重要而又迫切需要解决的技术难题。

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