And its source comes from an unlikely place: pond scum.

而这一方法的来源确是一个看似不可能的地方：池塘里的. .。

youdao

There was green scum over the pond.

池塘水面有绿色的浮藻。

youdao

There was green scum over the pond.

池塘水面有绿色的浮藻。

youdao