The answer is: [B]: "proportion" .
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Specifically, this refers to the Fibonacci series:
→ " 1:1:2:3:5:8:13......" ;
→ {Note: "bolded text" is for emphasis.}.
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Note: The sequence is written in "ratios" ; or "proportions" .
→ { hence; Answer choice: [B]: " proportions " . } .
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→ { Take note of the "colon" symbols used. } .
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