一些因素，比如吸烟和年龄大是女性流产可能的原因，但医生们通常并不能查明原因所在。

Some factors, like smoking and age, can contribute to the likelihood a woman might miscarry, but doctors usually can't pinpoint a reason.

youdao

一些因素，比如吸烟和年龄大是女性流产可能的原因，但医生们通常并不能查明原因所在。

Some factors like smoking and age can contribute to the likelihood a woman might miscarry but doctors usually can't pinpoint a reason.

youdao

另一方面，它还有一种保护的因素，因为它还与较低水平的高风险行为相联系，比如吸烟和酗酒。

"On the other hand it had a protective factor, because it was also related to lower levels of high risk behavior," which includes things such as smoking and drinking.

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Let's say you want to see how something like cigarette smoking is changing in the population and the rates of cigarette smoking, and you want to look at people every five years from 1970 to 2000.

比如你想知道,人群中吸烟者的人数变化,和吸烟者的比例,在1970年至2000年每五年的情况

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