At age 15, he 27 to devote his life to developing a biological explanation of knowledge.
答案：(D) set out
set out to V（立志要做……）為固定搭配，表示皮亞傑15歲立志投入知識的生物學解釋研究；put down（放下）、passed on（傳遞）、ended up（最終淪為）均不符合此處語意。
四個選項都是動詞加介副詞的片語，你會憑中文挑一個。
空格後面接的是 to devote his life to developing a biological explanation of knowledge（把一生投入於發展一套知識的生物學解釋）。所以空格要填的必須是一個後面能接不定詞、而且意思是「開始去做」的片語。set out to V 就是「著手去做、立志去做」，用在一個人決定投入某件長遠的事情上，正好對得上十五歲立定志向這個情境。填進去讀成 At age 15, he set out to devote his life to developing a biological explanation of knowledge。順帶留意 devote 後面那個 to 是介系詞，所以接的是 developing 而不是 develop——同一句裡兩個 to、詞性不同，這是常見的陷阱。
put down（放下；記下）後面接的是被放下或被寫下的東西；passed on（傳遞下去）後面接的是被傳遞的東西；ended up（最後落得）後面接的是 V-ing 或形容詞，不接不定詞，而且它講的是結果、不是起點。
set out to V（著手、立志去做）、devote oneself to ＋ V-ing（致力於做某事）、be devoted to ＋ 名詞（專注於）、end up ＋ V-ing（最後落得）、put down（放下；記下）、pass on（傳遞下去）。
Jean Piaget, a psychologist and pioneer in the study of child intelligence, was born in Switzerland in 1896. At age 10, he managed his first 26, a description of a partly albino sparrow he observed in a public park. At age 15, he 27 to devote his life to developing a biological explanation of knowledge.
He began his career as a zoologist, 28 mollusks and their adaptations to their environment. 29 age 21, he had already published 25 professional papers on that topic.
Later, after working with Alfred Binet in Paris, he became interested in levels of logic used by children taking standardized tests on intelligence. Piaget 30 to establish a body of psychology all his life and became a very influential figure in educational psychology. His works were all written originally in French and were later translated into English.