这一天，小冲浪有一个新问题：“Daddy, is coal expensive or cheap?”

哇，娃开始关心价钱了，是个好事哈。老大我就说，“Coal is not expensive and can be cheap.”

“How can coal be cheap?”小冲浪的好奇心棒棒的。

“For some open-pit coal mines, the coal is just lying there on the ground, waiting for an excavator to dig it up and put it in a dump chuck. This way, the coal can be 'dirt cheap'.”老大我解释。

“Oh, coal can be 'dirt cheap'.”小冲浪说，若有所悟。

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改天，小冲浪翻到他的一本书，上面有讲到一些biofuel，他很高兴地跟我说，“Daddy, biochar is 'tree cheap'!”

我听到了，想起来前些天聊'dirt cheap'来着，知道咱小冲浪又在练习举反了，就表扬他说，“Good phrase - tree cheap!”

燃后，大小冲浪都很开心地笑了。

2024.5