As feathers became larger over time, flapping flight evolved and birds finally became fully air-borne.

随着时间的推移，羽毛变得越来越大，扑翼飞行逐渐发展，鸟类最终完全可以在空中飞行。

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As feathers became larger over time, flapping flight evolved and birds finally became fully air-borne.

随着时间的推移，羽毛变得越来越大，扑翼飞行逐渐发展，鸟类最终完全可以在空中飞行。

youdao