To make the best cup of coffee, the ______ of brewing time to coffee beans and water has to be precise.

(a) portion

(b) ratio

(c) section

(d) division

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brew [bru]  v.  為……泡（茶），為……煮（咖啡）[O1]

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ratio   比；比率；【數】比例The ratio of students to teachers is 35: 1. 學生和老師的比率是三十五比一。

the ratio of A to B     A和B的比率

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