The sport's rules require that a race walker's knees stay straight through most of the leg swing and one foot remain in contact with the ground at all times.

这项运动的规则要求竞走运动员的膝盖在大部分的腿部摆动过程中保持笔直，一只脚始终与地面保持接触。

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Accounting rules require that investments are held at "fair value" -the price at which they can be sold to a third party in an orderly transaction.

会计准则规定，在一个有序交易下，投资人以“公允价值”的价格出售给第三方。

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California, home of Silicon Valley, recently proposed far more restrictive rules that would require human drivers be ready to take the wheel, and ban commercial use of self-driving technology.

硅谷之乡加州最近提出了更为严格的规定，要求人类驾驶员做好驾驶准备，并禁止将自动驾驶技术用于商业用途。

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The new rules require that less than 10% of the calories students consume in a meal come from saturated fat.

WSJ: School Lunches to Become Healthier

The existing work rules require that, on many routes, separate trucks must deliver the bread and cake products to that single customer location.

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The rules require that, over the next two school years, whole-grain products must account for half of the grain products served in school lunches.

WSJ: School Lunches to Become Healthier