But an oak which has fewer but bigger leaves with stronger reflections, produces a jagged wave form, or what we called a rough echo.

但是，橡树的叶子少而又大，反射力较强，会产生参差不齐的声波，或所谓的“粗糙回声”。

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The echo command expects one or more strings, so this line produces an error complaining about the missing closing quote on (what Vim assumes to be) the second string.

echo 命令要求一个或多个字符串，因此此行代码将生成一个错误，指出第二个字符串缺少一个右引号（Vim 是这样认为的）。

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