Anything from cosmic rays to radiation to diet may activate a dormant oncogene, but how remains unknown.

从宇宙射线、辐射到日常饮食，任何东西都可能激活一个处于静止状态下的致癌基因，但如何激活尚不为人知。

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How parental age increases autism risks remains unknown, but several hypotheses exist.

父母年龄是如何加大孤独症风险的仍是未知数，但存在一些假设。

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Much remains unknown about when and how quickly China is going to start pushing its currency higher. But for once, a rising currency could be good news in Japan.

中国将何时、以何种速度开始升值人民币，目前仍不清楚。不过，至少这次，人民币升值可能对日本来说是好消息。

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With these cards, consumers are given a revolving line of credit, but are encouraged to exceed it significantly (by how much remains unknown) as long as they pay off this excess amount each month.

FORBES: The Pitfalls of No Pre-Set Spending Limit Credit Cards

How or why this might happen remains unknown, but it may be due to competition between different mitochondrial strains within a cell.

ECONOMIST: Trojan DNA

Much still remains unknown about the virus, including how people are getting infected, but scientists say it contains genetic markers that could help it infect humans.

NPR: Bird Flu 101: How Bad Is The New H7N9 Strain?