使成为水平，使平坦，使平均。

To make horizontal, flat, or even.

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PRK是移除角膜薄的表层(上皮细胞)，然后眼科医生用激光使角膜平坦或弯曲。

PRK removes the thin surface layer of your cornea (epithelium). Your eye surgeon then USES a laser to flatten your cornea or make its curve steeper.

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在前往慕尼黑的旅途中，余下的旅程如梦一般美妙：平坦而标识清楚的自行车专用道，使我们轻而易举地在一天的时间里完成了从乌尔姆到慕尼黑的125英里旅程。

The remaining journey to Munich was a dream: well-signed and flat cycle routes blazed a trail so easy to follow that we were able to ride the 125 miles from Ulm to Munich in one day.

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