Interestingly, both of them 16 buying the same pair of jeans.
答案：(B) ended up
【句型】end up + V-ing 字詞搭配「最終/結果……」，表示「兩人最後都買了同一條牛仔褲」；gave up（放棄）、took to（愛上，通常搭配名詞或Ving表「開始喜歡」，語意不完全符合這裡）、used to（過去習慣，時態不合，這裡講的是這次購物的結果不是過去習慣）都不合。
四個都是常見的片語，代進去形狀差不多。used to 最誘人，因為「以前常買同一件牛仔褲」乍看說得通。但這裡就藏著課本上的老陷阱：used to 後面接原形動詞（used to buy），be used to 後面才接動名詞（be used to buying），兩個長得像，意思完全不同。
先看形式。空格後面是 buying，是動名詞。四個選項裡能直接接動名詞的是 end up、give up、take to；used to 要接原形，形式上先出局——真要接動名詞得寫成 were used to buying，意思也整個變了。再看語意。前一句說 Anita was shopping with her mother and enjoying it，接著這一句用 Interestingly（有趣的是）開頭——這個轉承語就是在預告一件出乎意料的事。母女倆逛街，最後買了同一件牛仔褲，正是「結果竟然…」。end up V-ing 的意思就是「最後落得…、結果變成…」（劍橋詞典），通常帶著「不是原本預期」的味道，和 Interestingly 完全合拍。這一句也是整篇的引子：後面整段在講年輕人的品味如何影響媽媽，母女買同一件牛仔褲就是這個現象的縮影。
gave up：放棄，give up buying 是「不買了」，與後文「年輕人影響購買決策」的主旨相反。took to：開始喜歡上、養成…的習慣，take to doing 講的是一段時間養成的愛好，不是這一次逛街的結果。used to：形式不合，語意也變成過去的習慣，與這次購物無關。
end up V-ing（最後結果變成…）、give up V-ing（放棄做…）、take to V-ing（開始喜歡上做…）、used to V（過去經常…）、be used to V-ing（習慣於做…）、a pair of jeans（一件牛仔褲）。
Anita was shopping with her mother and enjoying it. Interestingly, both of them 16 buying the same pair of jeans. According to a recent marketing study, young adults influence 88% of household clothing purchases. More often than not, those in their early twenties are the more 17 consumers. There isn't a brand or a trend that these young people are not aware of. That is why mothers who want to keep abreast of trends usually 18 the experts－their daughters. This tells the retailers of the world that if you want to get into a mother's 19 , you've got to win her daughter over first.
With a DJ playing various kinds of music rather than just rap, and a mix of clothing labels designed more for taste and fashion than for a precise age, department stores have managed to appeal to successful middle-aged women 20 losing their younger customers. They have created a shopping environment where the needs of both mother and daughter are satisfied.