Undulations
(undulation 的复数) n. 波动, 波状弯曲, 起伏\\n[医] 波动
🗣️ 情景例句
I guess I didn't have one, fortunately.
但我想我并没有，因为我的幸运的。
Let difficulties occur but not the loss of courage.
纵使困难重重，也不丧失勇气。
In this way, we have learned all that we know of the laws of astronomy,
例如，用这种方法，我们完全掌握了天文学的规律。