So American Airlines announced a new "value pricing" plan, which entailed cutting fares while replacing complex discounts with a simple, four-tier price system.

因此美国航空公司对外宣布了一个新的“定价”计划。这个计划在削减票价的同时，还用一个简明的四列价格体系取代复杂的打折程序。

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China a has a four-tier color-coded warning system for severe weather, with red being the most serious, followed by orange, yellow and blue.

中国对极端天气有一套四级预警系统，用四种颜色分别表示等级不同的预警，其中红色为最，其次是橙色、黄色和蓝色。 。

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China has a four-tier weather warning system, with red representing the most severe, followed by orange, yellow and blue.

中国有一套四个等级的天气预警系统，红色代表情况最为严重，其次是橙色、黄色和蓝色。

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Under the four-tier system, teachers will be rated exemplary, proficient, developing or below standard.

WSJ: Conn. Joining Teacher Trend

Teachers marked "ineffective" the lowest rating in a new four-tier system would get a second opinion by a third-party "validator" chosen by the union and the Department of Education.

WSJ: Teacher Evaluation Deal Reached

Under the new evaluation law, teachers are required to be ranked on a four-tier system based 40% on how much students have improved on tests or other measures, and 60% on more subjective measures, such as principals' observations.

WSJ: Teacher Evaluation Deal Falls Apart