Here in Africa, Lonsdorf is conducting one of the world's longest wildlife studies, trying to discover how learning is transferred 17 generations.
答案：(A) across
【介系詞】transferred across generations 表示「代代相傳」，across 表跨越（世代）之意，為此處慣用搭配。beside（在旁邊）、upon（在…之上）、within（在…之內）皆不符合文意。
across 這個字，你的印象大概只有走過馬路那個具體的動作（walk across the street），不太會想到它可以用在世代、族群這種抽象的範圍上。
答對率不到五成。先確定空格要的是什麼：is transferred 是被動，後面沒有受詞，所以空格填的是介系詞，帶出傳遞的範圍或方向。generations 是複數，講的是好幾個世代；學習要從上一代傳到下一代，跨越的是世代與世代之間，用 across（橫跨、遍及）。填進去讀成 how learning is transferred across generations（學習如何跨世代傳遞）。across 的具體義與這裡的抽象義是同一條線：都是從一邊到另一邊，只是這裡跨的不是馬路而是世代，這種「先有具體義、再往抽象推」的走法在介系詞題裡很常見。
beside（在……旁邊）講的是並排的位置，世代不是並排擺著的東西；upon 相當於較正式的 on，講的是接觸的表面或一發生就如何（upon arrival 一抵達），與傳遞的範圍無關；within（在……之內）方向剛好相反——它把範圍鎖在同一個世代裡面，但文章問的是上一代如何傳給下一代。
across generations（跨世代）、transfer A to B（把 A 傳遞給 B）、pass down（代代相傳）、within（在……範圍之內）、upon arrival（一抵達）、conduct a study（進行研究）。
Hiding herself among the trees near a chimpanzee habitat, Elizabeth Lonsdorf is using her camera to explore mysteries of learning. The chimpanzee she records picks up a thin flat piece of grass and then digs out tiny insects from a hole. Dinner is 16 ! But how did the chimp develop this ingenious skill with tools? Do the chimp babies copy their parents in using tools? Do the mothers most skilled with tools have offspring who are also good at using tools? Here in Africa, Lonsdorf is conducting one of the world's longest wildlife studies, trying to discover how learning is transferred 17 generations.
Lonsdorf has always been interested in animal learning and tool use, 18 the way young animals grow up and learn their way in the world. Her chimpanzee study shows a clear link between humans and the rest of the animal kingdom. The chimps make and use tools and have mother-child relationships very 19 to those of humans. Through observing chimpanzees' learning process, researchers hope to gain insight into what the development of our earliest ancestors 20 like.
Lonsdorf hopes that by understanding the complexity of animal behavior, we can better appreciate and protect the diversity of life on this planet.