21. Over the centuries, various theories have been advanced _____.
(A) the origin of alphabetic writing is explained
(B) of explaining the origin of alphabetic writing
(C) the explanation of the origin of alphabetic writing
(D) to explain the origin of alphabetic writing

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統計： A(2), B(5), C(4), D(29), E(0) #2327174

Astr

B1 · 2026/02/01

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Over the centuries, various theories have been advanced _________.

(D)to explain the origin of alphabetic writing.
幾個世紀以來，人們提出了各種理論來解釋字母文字的起源。

(A) the origin of alphabetic writing is explained ->若直接放在 advanced 後方會造成「雙動詞」錯誤，且缺乏連接詞。

(B) of explaining the origin of alphabetic writing of explaining -> of..通常接在名詞後當形容詞片語，advanced(被動態)後方需要是修飾動詞的表’目的’用語。

(D) to explain the origin of alphabetic writing -> 句子 "Theories have been advanced"（理論已被提出）。接在後是為了說明提出理論的’目的’， to + 原型動詞（不定詞）來表示「為了...」。

Advanced" 在這裡是被動語態。主動語態是 "People advance theories to explain..."。變成被動時，後方的 "to explain" 保持不變。