Nevertheless one had better know the rules, for they sometimes guide in doubtful cases, though not often.

然而一个人最好了解规则，因为有的时候人们会感到迷惑，尽管这种时候并不多。

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But in the architecture of Emperors 'tomb beds appeared more or less doubtful places, from which we can find some clues and uncover the historic cases of pendency.

但是，在帝王的陵寝建筑上或多或少地出现一些令人疑惑的地方，我们应该能够从中找到一些解开这些历史悬案的线索。

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In truly doubtful cases, only test crosses will reveal the actual genotype.

在确实可疑的情况下，只有通过杂交试验才能揭示出真正的基因型。

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The solution he proposes shows how much quotas could change Brazilians' sense of who they are: in doubtful cases a commission would verify students' racial identity, overthrowing the idea that a person's race is what he says it is.

ECONOMIST: Race in Brazil

By looking at large numbers of paintings that are universally believed to be authentic, Dr Farid hopes to be able to examine doubtful cases with confidence in the future.

ECONOMIST: Finding forgeries: Different strokes | The

In some cases the surgery itself is of doubtful value.

FORBES: Is elective surgery overdone?